  Alpha Miniloader Howto
  David A. Rusling, david.rusling@reo.mts.dec.com
  v0.84, 6 December 1996

  This document describes the Miniloader, a program for Alpha based sys­
  tems that can be used to initialize the machine and load Linux.  The
  Alpha Linux Miniloader (to give it it's full name) is also known as
  MILO.

  1.  Introduction

  This document describes the Miniloader for Linux on Alpha AXP (MILO).
  This firmware is used to initialize Alpha AXP based systems, load and
  start Linux and, finally, provide PALcode for Linux.

  1.1.  Copyright

  The Alpha Miniloader (MILO) HOWTO is copyright (C) 1995, 1996 David A
  Rusling.

  Copyright. Like all Linux HOWTO documents, it may be reproduced and
  distributed in whole or in part, in any medium, physical or
  electronic, so long as this copyright notice is retained on all
  copies.  Commercial redistribution is allowed and encouraged; however
  the author would like to be notified of such distributions.  You may
  translate this HOWTO into any language whatsover provided that you
  leave this copyright statement and disclaimer intact, and that you
  append a notice stating who translated the document.

  Disclaimer. While I have tried to include the most correct and up to
  date information available to me, I cannot guarantee that usage of
  information in this document does not result in loss of data or
  equipment.   I provide NO WARRENTY about the information in the HOWTO
  and I cannot be made liable for any consequences resulting from using
  the information in this HOWTO.

  1.2.  New Versions of this Document

  The latest version of this document can be found in
  <ftp://gatekeeper.dec.com/pub/Digital/Linux-Alpha/Miniloader/docs> and
  David Mosberger-Tang is kind enough to include the html form of it in
  his excellent Linux Alpha FAQ site
  <http://www.azstarnet.com/~axplinux>.

  2.  What is MILO?

  On Intel based PC systems, the BIOS firmware sets up the system and
  then loads the image to be run from the boot block of a DOS file
  system.  This is more or less what MILO does on an Alpha based system,
  however there are several interesting differences between BIOS
  firmware and MILO, not least of which is that MILO includes and uses
  standard Linux device drivers unmodified.  MILO is firmware, unlike
  LILO, which relies on the BIOS firmware to get itself loaded.  The
  main functional parts of MILO are:

  1. PALcode,

  2. Memory set up code (builds page tables and turns on virtual
     addressing),

  3. Video code (BIOS emulation code and TGA (21030)),

  4. Linux kernel code.  This includes real Linux kernel code (for
     example, the interrupt handling) and ersatz or mock Linux kernel,

  5. Linux block device drivers (for example, the floppy driver),

  6. File system support (ext2, MS-DOS and ISO9660),

  7. User inteface code (MILO),

  8. Kernel interface code (sets up the HWRPB and memory map for linux),

  9. NVRAM code for managing environment variables.

  The following paragraphs describe these functional parts in more
  detail.

  PALcode can be thought of as a tiny software layer that tailors the
  chip to a particular operating system.  It runs in a special mode
  (PALmode) which has certain restrictions but it uses the standard
  Alpha instruction set with just five extra instructions.  In this way,
  the Alpha chip can run such diverse operating systems as Windows NT,
  OpenVMS, Digital Unix and, of course, Linux.  The PALcode that MILO
  uses (and therefore Linux itself) is, like the rest of MILO, freeware.
  It is derived from Digital's Evaluation Board software example Digital
  Unix PALcode..  The differences between the different PALcodes are
  because of differences in address mapping and interrupt handling that
  exist between the Alpha chips (21066 based systems have a different
  I/O map to 21064+2107x systems) and different Alpha based systems.

  For MILO to operate properly it needs to know what memory is
  available, where Linux will eventually be running from and it must be
  able to allocate temporary memory for the Linux device drivers.  The
  code maintains a memory map that has entries for permanent and
  temporary allocated pages.  As it boots, MILO uncompresses itself into
  the correct place in physical memory.   When it passes control to the
  Linux kernel, it reserves memory for the compressed version of itself,
  the PALcode (which the kernel needs) and some data structures.  This
  leaves most of the memory in the system for Linux itself.

  The final act of the memory code is to set up and turn on virtual
  addressing so that the data structures that Linux expects to see are
  at the correct place in virtual memory.

  MILO contains video code that initialises and uses the video device
  for the system.  It will detect and use a VGA device if there is one,
  otherwise it will try to use a TGA (21030) video device.  Failing
  that, it will assume that there is no graphics device.  The BIOS
  emulation that the standard, pre-built, images include is Digital's
  own BIOS emulation which supports most, if not all, of the standard
  graphics devices available.

  Linux device drivers live within the kernel and expect certain
  services from the kernel.  Some of these services are provided
  directly by Linux kernel code, for example the interrupt handling and
  some is provided by kernel look-alike routines.

  MILO's most powerful feature is that you can embed unaltered Linux
  device drivers into it.  This gives it the potential to support every
  device that Linux does.  MILO includes all of the block devices that
  are configured into the Linux kernel that it is built against as well
  as a lot of the block device code (for example, ll_rw_blk()).

  MILO loads the Linux kernel from real file systems rather than  from
  boot blocks and other strange places.  It understands MSDOS, EXT2 and
  ISO9660 filesystems.  Gzip'd files are supported and these are
  recommended, particularly if you are loading from floppy which is
  rather slow.  MILO recognises these by their .gz suffix.

  Built into MILO is a simple keyboard driver which, together with an
  equally simple video driver allows it to have a simple user interface.
  That interface allows you to list file systems on configured devices,
  boot Linux or run flash update utilities and set environment variables
  that control the system's booting.  Like LILO, you can pass arguments
  to the Kernel.

  MILO must tell the Linux kernel what sort of system this is, how much
  memory there is and which of that memory is free.  It does this using
  the HWRPB (Hardware Restart Parameter Block) data structure and
  associated memory cluster descriptions.  These are placed at the
  appropriate place in virtual memory just before control is passed to
  the Linux kernel.

  3.  Pre-Built Standard MILO Images.

  If you are planning to run Linux on a standard Alpha based system,
  then there are pre-built "standard" MILO images that you might use.
  These (along with the sources and other interesting stuff) can be
  found in <ftp://gatekeeper.dec.com/pub/Digital/Linux-
  Alpha/Miniloader>.

  The images subdirectory contains a directory per standard system (eg
  AlphaPC64) with MILO images having the following naming convention:

  1. MILO - Miniloader executable image, this image can be loaded in a
     variety of ways,

  2. fmu.gz - Flash management utility,

  3. MILO.dd - Boot block floppy disk image.  These should be written
     using rawrite.exe or dd on Linux.

  The test-images, like the images subdirectory contains a directory per
  standard system.   These images are somewhat experimental but tend to
  contain all the latest features.

  4.  How To Build MILO

  You build MILO seperately from the Kernel.  As MILO requires parts of
  the kernel to function (for example interrupt handling) you must first
  configure and build the kernel that matches with MILO that you want to
  build.  Mostly this means building the kernel with the same version
  number.  So, MILO-2.0.25.tar.gz will build against
  linux-2.0.25.tar.gz.  MILO may build against a higher version of the
  kernel, but there again it may not.  Also, now that ELF shared
  libraries are fully supported, there are two versions of the MILO
  sources.  To build under an ELF system you must first unpack the
  standard MILO sources and then patch those sources with the same
  version numbered ELF patch.  In the remainder of this discussion, I
  assume that your kernel sources and object files are stored in the
  subtree at /usr/src/linux and that the linux kernel has been fully
  built with the command make boot

  To build MILO, change your working directory to the MILO source
  directory and invoke make with:

       $    make KSRC=/usr/src/linux config

  Just like the Linux kernel, you will be asked a series of questions

            Echo output to the serial port (MINI_SERIAL_ECHO) [y]

  It's a good idea to echo kernel printk to /dev/ttyS0 if you can.  If
  you can (and want to), then type "y", otherwise "n".  All of the
  standard, pre-built, MILO images include serial port I/O using COM1.

            Use Digital's BIOS emulation code (not free) (MINI_DIGITAL_BIOS_EMU) [y]

  This code is included as a library which is freely distributable so
  long as it is used on an Alpha based system.  The sources are not
  available.   If you answer n then the freeware alternative BIOS
  emulation will be built.  It's sources are included with MILO.  Note
  that you cannot right now build choose Digital's BIOS emulation code
  in an ELF system (the library is not yet ready) and so you must answer
  no to this question.

            Build PALcode from sources (Warning this is dangerous) (MINI_BUILD_PALCODE_FROM_SOURCES) [n]

  You should only do this if you have changed the PALcode sources,
  otherwise use the standard, pre-built PALcode included with MILO.

  You are now all set to build the MILO image itself:

  $    make KSRC=/usr/src/linux

  When the build has successfully completed, the MILO image is in the
  file called milo.  There are a lot of images called milo.*, these
  should be ignored.

  5.  How To Load MILO

  The most commonly supported method of loading MILO is from the Windows
  NT ARC firmware as most shipping systems support this.  However, there
  are a wide variety of  loading MILO.   It may be loaded from:

  ·  a failsafe boot block floppy,

  ·  the Windows NT ARC firmware,

  ·  Digital's SRM console,

  ·  an Alpha Evaluation Board Debug Monitor,

  ·  flash/ROM.

  5.1.  Loading MILO from the Windows NT ARC firmware

  Most, if not all, Alpha AXP based systems include the Windows NT ARC
  firmware and this is the prefered method of booting MILO and thus
  Linux.  Once the Windows NT firmware is running and you have the
  correct MILO image for your system, this method is completely generic.

  The Windows NT ARC firmware is an environment in which programs can
  run and make callbacks into the firmware to perform actions.  The
  Windows NT OSLoader is a program that does exactly this.   Linload.exe
  is a much simpler program which does just enough to load and execute
  MILO.  It loads the appropriate image file into memory at 0x00000000
  and then makes a swap-PAL PALcall to it.  MILO, like Linux, uses a
  different PALcode to Windows NT which is why the swap has to happen.
  MILO relocates itself to 0x200000 and continues on through the PALcode
  reset entry point as before.

  Before you add a Linux boot option, you will need to copy linload.exe
  and the appropriate MILO that you wish to load to someplace that the
  Windows NT ARC firmware can read from.  In the following example, I
  assume that you are booting from a DOS format floppy disk:

  1. At the boot menu, select "Supplementary menu..."

  2. At the "Supplementary menu", select "Set up the system..."

  3. At the "Setup menu", select "Manage boot selection menu..."

  4. In the "Boot selections menu", choose "Add a boot selection"

  5. Choose "Floppy Disk 0"

  6. Enter "linload.exe" as the osloader directory and name

  7. Say "yes" to the operating system being on the same partition as
     the osloader

  8. Enter "

  9. I usually enter "Linux" as the name for this boot selection

  10.
     Say "No" you do not want to initialise the debugger at boot time

  11.
     You should now be back in the "Boot selections menu", choose the
     "Change a boot selection option" and pick the selection you just
     created as the one to edit

  12.
     Use the down arrow to get "OSLOADFILENAME" up and then type in the
     name of the MILO image that you wish to use, for example
     "noname.arc" followed by return.

  13.
     Press ESC to get back to the "Boot Selections menu"

  14.
     Choose "Setup Menu" (or hit ESC again) and choose "Supplementary
     menu, and save changes" option

  15.
     ESC will get you back to the "Boot menu" and you can attempt to
     boot MILO.  If you do not want Linux as the first boot option, then
     you can alter the order of the boot options in the "Boot selections
     menu".

  At the end of all this, you should have a boot selection that looks
  something like:

       LOADIDENTIFIER=Linux
       SYSTEMPARTITION=multi(0)disk(0)fdisk(0)
       OSLOADER=multi(0)disk(0)fdisk(0)\linload.exe
       OSLOADPARTITION=multi(0)disk(0)fdisk(0)
       OSLOADFILENAME=\noname.arc
       OSLOADOPTIONS=

  You can now boot MILO (and then Linux).  You can load linload.exe and
  MILO directly from a file system that Windows NT understands such as
  NTFS or DOS on a hard disk.

  The contents OSLOADOPTIONS are passed to MILO which interprets it as a
  command.   So, in order to boot Linux directly from Windows NT without
  pausing in MILO, you could pass the following in OSLOADOPTIONS:

       boot sda2:vmlinux.gz root=/dev/sda2

  See ``MILO's User Interface'' for more information on the commands
  available.

  Another (rather sneaky) way of loading of loading MILO via the WNT ARC
  firmware is to put MILO onto an MS-DOS floppy and call it fwupdate.exe
  and then choose the "Upgrade Firmware" option.

  5.2.  Loading MILO from the Evaluation Board Debug Monitor

  Evaluation boards (and often designs cloned from them) include support
  for the Alpha Evaluation Board Debug Monitor.   Consult your system
  document before considering this method of booting MILO.   The
  following systems are known to include Debug Monitor support:

  ·  AlphaPC64 (Section ``AlphaPC64'')

  ·  EB64+ (Section ``EB64+'')

  ·  EB66+ (Section ``EB66+'')

  ·  EB164 (Section ``EB164'')

  ·  PC164 (Section ``PC164'')

  Before you consider this method, you should note that the early
  versions of the Evaluation Board Debug Monitor did not include video
  or keyboard drivers and so you must be prepared to connect another
  system via the serial port so that you can use the Debug Monitor.  Its
  interface is very simple and typing help shows a whole heap of
  commands.  The ones that are most interesting include the word boot or
  load in them.

  The Evaluation Board Debug Monitor can load an image either via the
  network (netboot) or via a floppy (flboot).  In either case, set the
  boot address to 0x200000 (> bootadr 200000) before booting the image.

  If the image is on floppy (and note that only DOS formatted floppies
  are supported), then you will need to type the following command:

            AlphaPC64> flboot <MILO-image-name>

  5.3.  Loading MILO from a Failsafe Boot Block Floppy

  Only the AxpPCI33 is known to include failsafe boot block floppy
  support (Section < id="noname-section" name="Noname">).

  If you do not have a standard pre-built MILO .dd image, then you may
  need to build an SRM boot block floppy.  Once you have built MILO, you
  need to do the following on Digital Unix box:

       fddisk -fmt /dev/rfd0a
       cat mboot bootm > /dev/rfd0a
       disklabel -rw rfd0a 'rx23' mboot bootm

  Or on a Linux box:

            cat mboot bootm > /dev/fd0

  If you have a standard MILO image available (say MILO.dd) then you
  would build a boot block floppy using the following command:

            dd if=MILO.dd of=/dev/fd0

  5.4.  Loading MILO from Flash

  There are a number of systems where MILO can be blown into flash and
  booted directly (instead of via the Windows NT ARC firmware):

  ·  AlphaPC64 (Section ``AlphaPC64'')

  ·  Noname (Section ``Noname'')

  ·  EB66+ (Section ``EB66+'')

  ·  EB164 (Section ``EB164'')

  ·  PC164 (Section ``PC164'')

  5.5.  Loading MILO from the SRM Console

  The SRM (short for System Reference Manual) Console knows nothing
  about filesystems or disk-partitions, it simply expects that the
  secondary bootstrap loader occupies a consecutive range of physical
  disk sectors starting from a given offset.   The information
  describing the secondary bootstrap loader (its size and offset) is
  given in the first 512 byte block.   To load MILO via the SRM you must
  generate that structure on a device which the SRM can access (such as
  a floppy disk).  This is what mboot and bootm, mboot is the first
  block (or boot description) and mboot is the MILO image rounded up to
  a 512 byte boundary.

  To load MILO from a boot block device, either build mboot and bootm
  and push them onto the boot device using the following command:

               $ cat mboot bootm > /dev/fd0

  Or, grab the appropriate MILO.dd from a web site and write it onto the
  boot device using either RAWRITE.EXE or dd.

  Once you have done that you can boot the SRM console and use one of
  its many commands to boot MILO.   For example, to boot MILO from a
  boot block floppy you would use the following command:

               >>>boot dva0
               (boot dva0.0.0.0.1 -flags 0)
               block 0 of dva0.0.0.0.1 is a valid boot block
               reading 621 blocks from dva0.0.0.0.1
               bootstrap code read in
               base = 112000, image_start = 0, image_bytes = 4da00
               initializing HWRPB at 2000
               initializing page table at 104000
               initializing machine state
               setting affinity to the primary CPU
               jumping to bootstrap code
               MILO Stub: V1.1
               Unzipping MILO into position
               Allocating memory for unzip
               ####...

  The following systems are known to have SRM Console support:

  ·  Noname (Section ``Noname'')

  ·  AlphaPC64 (Section ``AlphaPC64'')

  ·  EB164 (Section ``EB164'')

  ·  PC164 (Section ``PC164'')

  5.6.  System Specific Information

  5.6.1.  AxpPCI33 (Noname)

  The Noname board can load MILO from the Windows NT ARC firmware
  (Section ``booting from Windows NT ARC firmware''), from the SRM
  Console (Section ``Loading MILO from the SRM Console'').  and from a
  failsafe boot block floppy (Section ``Loading from a Failsafe Boot
  Block Floppy'').  A flash management utility, runnable from MILO is
  available so that once MILO is running, it can be blown into flash
  (Section ``running the flash management utility'').  However, be
  warned that once you have done this you will lose the previous image
  held there as there is only room for one image.

  The way that Noname boots is controlled by a set of jumpers on the
  board, J29 and J28.  These look like:

                      4
          J29     2 x x x 6
                  1 x x x 5

          J28     2 x x x 6
                  1 x x x 5
                      3

  The two options that we're interested in are J28, pins 1-3 which boots
  the console/loader from flash and J29, pins 1-3 which boots the
  console/loader from a boot block floppy.  The second option is the one
  that you need to first boot MILO on the Noname board.

  Once you've selected the boot from floppy option via the jumpers, put
  the SRM boot block floppy containing MILO into the floppy and reboot.
  In a few seconds (after the floppy light goes out) you should see the
  screen blank to white and MILO telling you what's going on.

  If you are really interested in technical stuff, the Noname loads
  images off of the floppy into physical address 0x104000 and images
  from flash into 0x100000.  For this reason, MILO is built with it's
  PALcode starting at 0x200000.  When it is first loaded, it moves
  itself to the correct location (see relocate.S).

  5.6.2.  AlphaPC64 (Cabriolet)

  The AlphaPC64 includes the Windows NT ARC firmware (Section ``booting
  from Windows NT ARC firmware''), the SRM Console (Section ``Loading
  MILO from the SRM Console'') and the Evaluation Debug Monitor (Section
  ``Loading from the Debug Monitor'').  These images are in flash and
  there is room to add MILO so that you can boot MILO directly from
  flash.  A flash management utility, runnable from MILO is available so
  that once MILO is running, it can be blown into flash (Section
  ``running the flash management utility'').  This system supports MILO
  environment variables.

  You select between the boot options (and MILO when it is been put into
  flash) using a combination of jumpers and a boot option which is saved
  in the NVRAM of the TOY clock.

  The jumper is J2, SP bits 6 and 7 have the following meanings:

  ·  SP bit 6 should always be out.  If this jumper is set then the SROM
     mini-debugger gets booted,

  ·  SP bit 7 in is boot image selected by the boot option byte in the
     TOY clock,

  ·  SP bit 7 out is boot first image in flash.

  So, with bit 7 out, the Debug Monitor will be booted as it is always
  the first image in flash.  With bit 7 in, the image selected by the
  boot option in the TOY clock will be selected.  The Debug Monitor, the
  Windows NT ARC firmware and MILO all support setting this boot option
  byte but you must be very careful using it.  In particular, you cannot
  set the boot option so that next time the system boots MILO when you
  are running the Windows NT ARC firmware, it only allows you to set
  Debug Monitor or Windows NT ARC as boot options.
  To get MILO into flash via the Evaluation Board Debug Monitor, you
  will need a flashable image.  The build proceedures make MILO.rom, but
  you can also make a rom image using the makerom tool in the Debug
  Monitor software that comes with the board:

      > makerom -v -i7 -l200000 MILO -o mini.flash

  (type makerom to find out what the arguments mean, but 7 is a flash
  image id used by the srom and -l200000 gives the load address for the
  image as 0x200000).

  Load that image into memory (via the Debug Monitor commands flload,
  netload, and so on) at 0x200000 and then blow the image into flash:

            AlphaPC64> flash 200000 8

  (200000 is where the image to be blown is in memory and 8 is the
  segment number where you put the image.   There are 16 1024*64 byte
  segments in the flash and the Debug Monitor is at seg 0 and the
  Windows NT ARC firmware is at seg 4).

  Set up the image that the srom will boot by writing the number of the
  image into the TOY clock.

            AlphaPC64> bootopt 131

  (131 means boot the 3rd image, 129 = 1st, 130 = 2nd and so on).

  Power off, put jumper 7 on and power on and you should see the MILO
  burst into life.  If you don't then take jumper 7 back off and reboot
  the Debug Monitor.

  5.6.3.  EB66+

  The EB66+, like all of the Alpha Evaluation Boards built by Digital
  contains the Evaluation Board Debug Monitor and so this is available
  to load MILO (Section ``Loading from the Debug Monitor'').  Quite
  often (although not always) boards whose design is derived from these
  include the Debug Monitor also.  Usually, these boards include the
  Windows NT ARC firmware (Section ``booting from Windows NT ARC
  firmware'').  A flash management utility, runnable from MILO is
  available so that once MILO is running, it can be blown into flash
  (Section ``running the flash management utility'').  This system
  supports MILO environment variables.

  These systems have several boot images in flash controlled by jumpers.
  The two jumper banks are J18 and J16 and are located at the bottom of
  the board in the middle (if the Alpha chip is at the top).  You select
  between the boot options (and MILO when it is been put into flash)
  using a combination of jumpers and a boot option which is saved in the
  NVRAM of the TOY clock.

  Jumper 7-8 of J18 in means boot the image described by the boot
  option.   Jumper 7-8 of J18 out means boot the Evaluation Board Debug
  Monitor.

  Blowing an image into flash via the Evaluation Board Debug Monitor is
  exactly the same proceedure as for the AlphaPC64 (Section
  ``AlphaPC64'').

  5.6.4.  EB64+/Aspen Alpine

  This system is quite like the AlphaPC64 except that it does not
  contain flash which MILO can be loaded from.  The EB64+ has two ROMs,
  one of which contains the Windows NT ARC firmware (Section ``booting
  from Windows NT ARC firmware'').  and the other contains the
  Evaluation Board Debug Monitor (Section ``Loading from the Debug
  Monitor'').

  The Aspen Alpine is a little different in that it only has one ROM;
  this contains the Windows NT ARC firmware.

  5.6.5.  Universal Desktop Box (Multia)

  This is a very compact pre-packaged 21066 based system that includes a
  TGA (21030) graphics device.   Although you can just fit a half height
  PCI graphics card in the box you are better off waiting for full TGA
  support in XFree86.   It includes the Windows NT ARC firmware and so
  booting from that is the prefered method (Section ``Loading from
  Windows NT'').

  5.6.6.  EB164

  The EB164, like all of the Alpha Evaluation Boards built by Digital
  contains the Evaluation Board Debug Monitor and so this is available
  to load MILO (Section ``Loading from the Debug Monitor'').  Quite
  often (although not always) boards whose design is derived from these
  include the Debug Monitor also.  Usually, these boards include the
  Windows NT ARC firmware (Section ``booting from Windows NT ARC
  firmware'').  The SRM console is also available (Section ``Loading
  MILO from the SRM Console'').  A flash management utility, runnable
  from MILO is available so that once MILO is running, it can be blown
  into flash (Section ``running the flash management utility'').  This
  system supports MILO environment variables.

  These systems have several boot images in flash controlled by jumpers.
  The two jumper bank is J1 and is located at the bottom of the board on
  the left (if the Alpha chip is at the top).  You select between the
  boot options (and MILO when it is been put into flash) using a
  combination of jumpers and a boot option which is saved in the NVRAM
  of the TOY clock.

  Jumper SP-11 of J1 in means boot the image described by the boot
  option.   Jumper SP-11 of J1 out means boot the Evaluation Board Debug
  Monitor.

  Blowing an image into flash via the Evaluation Board Debug Monitor is
  exactly the same proceedure as for the AlphaPC64 (Section
  ``AlphaPC64'').

  5.6.7.  PC164

  The PC164, like all of the Alpha Evaluation Boards built by Digital
  contains the Evaluation Board Debug Monitor and so this is available
  to load MILO (Section ``Loading from the Debug Monitor'').  Quite
  often (although not always) boards whose design is derived from these
  include the Debug Monitor also.  Usually, these boards include the
  Windows NT ARC firmware (Section ``booting from Windows NT ARC
  firmware'').  The SRM console is also available (Section ``Loading
  MILO from the SRM Console'').  A flash management utility, runnable
  from MILO is available so that once MILO is running, it can be blown
  into flash (Section ``running the flash management utility'').  This
  system supports MILO environment variables.

  These systems have several boot images in flash controlled by jumpers.
  The main jumper block, J30, contains the system configuration jumpers
  and jumper CF6 in means that the system will boot the Debug Monitor,
  the default is out.

  Blowing an image into flash via the Evaluation Board Debug Monitor is
  exactly the same proceedure as for the AlphaPC64 (Section
  ``AlphaPC64'').

  5.6.8.  XL266

  The XL266 is one of a family of systems that are known as Avanti.  It
  has a riser card containing the Alpha chip and cache which plugs into
  the main board at right angles.   This board can replace the
  equivalent Pentium board.

  Some of these systems ship with the SRM console but others, notably
  the XL266 ship with only the Windows NT ARC firmware (Section
  ``booting from Windows NT ARC firmware'').

  Here is my list of compatible systems:

  ·  AlphaStation 400 (Avanti),

  ·  AlphaStation 250,

  ·  AlphaStation 200 (Mustang),

  ·  XL.  There are two flavours, XL266 and XL233 with the only
     difference being in processor speed and cache size.

  Note The system that I use to develop and test MILO is an XL266 and so
  this is the only one that I can guarentee will work.  However,
  technically, all of the above systems are equivalent; they have the
  same support chipsets and the same interrupt handling mechanisms.

  5.6.9.  Platform2000

  This is a 233Mhz 21066 based system.

  6.  MILO's User Interface

  Once you have correctly installed/loaded/run MILO you will see the
  MILO (for MIniLOader) prompt displayed on your screen.  There is a
  very simple interface that you must use in order to boot a particular
  Linux kernel image.  Typing "help" is a good idea as it gives a useful
  summary of the commands.

  6.1.  The ''help'' Command

  Probably the most useful command that MILO has:

       MILO> help
       MILO command summary:

       ls [-t fs] [dev:[dir]]
                           - List files in directory on device
       boot [-t fs] [dev:file] [boot string]
                           - Boot Linux from the specified device and file
       run [-t fs] dev:file
                           - Run the standalone program dev:file
       show                - Display all known devices and file systems
       set VAR VALUE       - Set the variable VAR to the specified VALUE
       unset VAR           - Delete the specified variable
       reset               - Delete all variables
       print               - Display current variable settings
       help [var]          - Print this help text

       Devices are specified as: fd0, hda1, hda2, sda1...
       Use the '-t filesystem-name' option if you want to use
         anything but the default filesystem  ('ext2').
       Use the 'show' command to show known devices and filesystems.
       Type 'help var' for a list of variables.

  Note that the bootopt command only appears on AlphaPC64 (and similar)
  systems.  Refer to the board's dcoumentation to find out just what it
  means.

  Devices.  Until you use a command that needs to make use of a device,
  no device inititalisation will take place.   The first show, ls, boot
  or run commands all cause the devices within MILO to be initialised.
  Devices are named in the same way (exactly) that Linux itself will
  name them.  So, the first IDE disk will be called 'hda' and it's first
  partition will be 'hda1'.  Use the show command to show what devices
  are available.

  File Systems.   MILO supports three file systems, MSDOS, EXT2 and
  ISO9660.  So long as a device is available to it, MILO can listboot or
  run an image stored on one of these file systems.  MILO's default file
  system is EXT2 and so you have tell MILO that the file system is
  something other than that.  All of the commands that use filenames
  allow you to pass the file system using the -t [filesystem]option.
  So, if you wanted to list the contents of a SCSI CD ROM, you might
  type the following:

            MILO> ls -t iso9660 scd0:

  Variables.  MILO contains some settable variables that help the boot
  process.  If you are loading via the Windows NT ARC firmware, then
  MILO makes use of the boot option environment variables set up by that
  firmware.  For some systems, MILO (for example, the AlphaPC64)
  maintains its own set of environment variables that do not change from
  boot to boot.  These variables are:

       MILO> help var
       Variables that MILO cares about:
         MEMORY_SIZE      - System memory size in megabytes
         BOOT_DEV         - Specifies the default boot device
         BOOT_FILE        - Specifies the default boot file
         BOOT_STRING      - Specifies the boot string to pass to the kernel
         SCSIn_HOSTID     - Specifies the host id of the n-th SCSI controller.
         AUTOBOOT         - If set, MILO attempts to boot on powerup
                            and enters command loop only on failure.
         AUTOBOOT_TIMEOUT - Seconds to wait before auto-booting on powerup.

  6.2.  Booting Linux

  The boot command boots a linux kernel from a device.  You will need to
  have a linux kernel image on an EXT2 formated disk (SCSI, IDE or
  floppy) or an ISO9660 formatted CD available to MILO.  The image can
  be gzip'd and in this case MILO will recognise that it is gzip'd by
  the .gz suffix.

  You should note that the version of MILO does not usually have to
  match the version of the Linux kernel that you are loading.  You boot
  Linux using the following command syntax:

            MILO> boot [-t file-system] device-name:file-name [[boot-option] [boot-option] ...]

  Where device-name is the name of the device that you wish to use and
  file-name is the name of the file containing the Linux kernel.   All
  arguments supplied after the file name are passed directly to the
  Linux kernel.

  If you are installing Red Hat, then you will need to specify a root
  device and so on.  So you would use:
            MILO> boot fd0:vmlinux.gz root=/dev/fd0 load_ramdisk=1

  MILO will automatically contain the block devices that you configure
  into your vmlinux.  I have tested the floppy driver, the IDE driver
  and a number of SCSI drivers (for example, the NCR 810), and these
  work fine.  Also, it is important to set the host id of the SCSI
  controller to a reasonable value.  By default, MILO will initialize it
  to the highest possible value (7) which should normally work just
  fine.  However, if you wish, you can explicitly set the host id of the
  n-th SCSI controller in the system by setting environment variable
  SCSIn_HOSTID to the appropriate value.  For example, to set the hostid
  of the first SCSI controller to 7, you can issue the following command
  at the MILO prompt:

            setenv SCSI0_HOSTID 7

  6.3.  Rebooting Linux

  You may want to reboot a running Linux system using the shutdown -r
  now command.  In this case, the Linux kernel returns control to MILO
  (via the HALT CallPAL entrypoint).  MILO leaves a compressed copy of
  itself in memory for just this reason and detects that the system is
  being rebooted from information held in the HWRPB (Hardware Restart
  Parameter Block).  In this case it starts to reboot using exactly the
  same command that was used to boot the Linux kernel the last time.
  There is a 30 second timeout that allows you to interrupt this process
  and boot whatever kernel you wish in whatever way you wish.

  6.4.  The ''bootopt'' command

  For flash based systems such as the AlphaPC64, EB164 and the EB66+,
  there are a number of possible boot options and these are changed
  using the bootopt command.  This has one argument, a decimal number
  which is the type of the image to be booted the next time the system
  is power cycled or reset:

  0 Boot the Evaluation Board Debug Monitor,

  1 Boot the Windows NT ARC firmware.

  In order to tell the boot code to boot the MILO firmware from flash
  then you need a boot option that means boot the N'th image.  For this,
  you need to 128 plus N, so if MILO is the third image, you would use
  the command:

            MILO> bootopt 131

  Note: Be very careful with this command.   A good rule is never to set
  bootopt to 0 (the Evaluation Board Debug Monitor), but instead use the
  system's jumpers to achieve the same thing.

  7.  Running the Flash Management Utility

  The run command is used to run the flash management utility.  Before
  you start you will need a device available to MILO that contains the
  updateflash program.  This (like vmlinux) can be gzip'd.  You need to
  run the flash management utility  program from the MILO using the
  (run) command:

            MILO> run fd0:fmu.gz

  Once it has loaded and initialised, the flash management utility will
  tell you some information about the flash device and give you a
  command prompt.  Again the help command is most useful.

       Linux MILO Flash Management Utility V1.0

       Flash device is an Intel 28f008SA
         16 segments, each of 0x10000 (65536) bytes
       Scanning Flash blocks for usage
       Block 12 contains the environment variables
       FMU>

  Note that on systems where environment variables may be stored and
  where there is more than one flash block (for example, the AlphaPC64)
  the flash management utility will look for a block to hold MILO's
  environment variables.  If such a block already exists, the flash
  management utility will tell you where it is.  Otherwise, you must use
  the environment command to set a block and initialise it.  In the
  above example, flash block 12 contains MILO's environment variables.

  7.1.  The ''help'' command

       FMU> help
       FMU command summary:

       list                - List the contents of flash
       program             - program an image into flash
       quit                - Quit
       environment         - Set which block should contain the environment variables
       bootopt num         - Select firmware type to use on next power up
       help                - Print this help text
       FMU>

  Note that the environment and bootopt commands are only available on
  the EB66+, the AlphaPC64, EB164 and PC164 systems (and their clones).

  7.2.  The ''list'' command

  The ''list'' command shows the current usage of the flash memory.
  Where there is more than one flash block, the usage of each flash
  block is shown.   In the example below you can see that Windows NT ARC
  is using blocks 4:7 and block 15.

       FMU> list
       Flash blocks:  0:DBM  1:DBM  2:DBM  3:WNT  4:WNT  5:WNT  6:WNT  7:WNT  8:MILO
               9:MILO 10:MILO 11:MILO 12:MILO 13:U 14:U 15:WNT
       Listing flash Images
         Flash image starting at block 0:
           Firmware Id:  0 (Alpha Evaluation Board Debug Monitor)
           Image size is 191248 bytes (3 blocks)
           Executing at 0x300000
         Flash image starting at block 3:
           Firmware Id:  1 (Windows NT ARC)
           Image size is 277664 bytes (5 blocks)
           Executing at 0x300000
         Flash image starting at block 8:
           Firmware Id:  7 (MILO/Linux)
           Image size is 217896 bytes (4 blocks)
           Executing at 0x200000
       FMU>

  7.3.  The ''program'' command

  The flash management utility contains a compressed copy of a flash
  image of MILO.  The ''program'' command allows you to blow this image
  into flash.  The command allows you to back out, but before you run it
  you should use the ''list'' command to see where to put MILO.  If MILO
  is already in flash, then the flash management utility will offer to
  overwrite it.

       FMU> program
       Image is:
           Firmware Id:  7 (MILO/Linux)
           Image size is 217896 bytes (4 blocks)
           Executing at 0x200000
       Found existing image at block 8
       Overwrite existing image? (N/y)? y
       Do you really want to do this (y/N)? y
       Deleting blocks ready to program: 8 9 10 11
       Programming image into flash
       Scanning Flash blocks for usage
       FMU>

  Wait until it has completed before powering off your system.

  Note: I cannot emphasise just how careful you must be here not to
  overwrite an existing flash image that you might need or render your
  system useless.   A very good rule is never to overwrite the Debug
  Monitor.

  7.4.  The ''environment'' command

  This selects a flash block to contain MILO's environment variables.

  7.5.  The ''bootopt'' command

  This is just the same as MILO's ''bootopt'' command, see (Section
  ``The ''bootopt'' command'').

  7.6.  The ''quit'' command

  This is really pretty meaningless.  The only way back to MILO (or
  anything else) once the flash management utility has run is to reboot
  the system.

  8.  Restrictions.

  Unfortunately this is not a perfect world and there, as always, some
  restrictions that you should be aware of.

  MILO is not meant to load operating systems other than Linux, although
  it can load images linked to run at the same place in memory as Linux
  (which is 0xFFFFFC0000310000).  This is how the flash management
  utilities can be run.

  The PALcode sources included in miniboot/palcode/blah are correct,
  however there are problems when they are built using the latest gas.
  They do build if you use the ancient a.out gas that's supplied in the
  Alpha Evaluation Board toolset (and that's how they were built).  I'm
  trying to get someone to fix the new gas.  Meanwhile, as a workaround,
  I have provided pre-built PALcode for the supported boards and David
  Mosberger-Tang has a fixed gas on his ftp site.

  9.  Problem Solving.

  Here are some common problems that people have seen, together with the
  solutions.

  Reading MS-DOS floppies from the Evaluation Board Debug Monitor.

  Some of the older versions of the Evaluation Board Debug Monitor (pre-
  version 2.0) have a problem with DOS format flopies generated from
  Linux.  Usually, the Debug Monitor can load the first few sectors all
  right, but then goes into an endless loop complaining about "bad
  sectors."  Apparently, there is an incompatibility between the DOS
  file system as expected by the Debug Monitor and the Linux
  implementation of DOSFS.  To make the long story short: if you run
  into this problem, try using DOS to write the floppy disk.  For
  example, if loading the file MILO.cab doesn't work, use a DOS machine,
  insert the floppy and then do:

       copy a:MILO.cab c:
       copy c:MILO.cab a:
       del c:MILO.cab

  Then try booting from that floppy again.  This normally solves the
  problem.

  MILO displays a long sequence of O> and does not accept input.

  This usually happens when MILO was built to use COM1 as a secondary
  console device.   In such a case, MILO echo output to COM1 and accepts
  input from there also.   This is great for debugging but not so great
  if you have a device other than a terminal connected.  If this
  happens, disconnect the device or power it down until the Linux kernel
  has booted.  Once Linux is up and running, everything will work as
  expected.

  MILO complains that the kernel image has the wrong magic number

  Older versions of MILO did not support the ELF object file format and
  so could not recognise an ELF image and this might be your problem.
  If this is reported, upgrade to the latest MILO that you can find.
  All 2.0.20 and beyond MILOs support ELF.  On the other hand it could
  be that the image is indeed damaged.  You should also note that MILO
  does not yet automatically distinquish between GZIP'd and non-GZIP'd
  images; you need to add the ".gz" suffix to the file name.

  MILO prints "...turning on virtual addressing and jumping to the Linux
  Kernel" and nothing else happens

  One obvious problem is that the kernel image is wrongly built or is
  built for another Alpha system altogether.  Another is that the video
  board is a TGA (Zlxp) device and the kernel has been built for a VGA
  device (or vice versa).  It is worth building the kernel to echo to
  COM1 and then connecting a terminal to that serial port or retrying
  the kernel that came with the Linux distribution that you installed.

  MILO does not recognise the SCSI device

  The standard MILO images include as many device drivers as are known
  to be stable for Alpha (as of now that includes the NCR 810, QLOGIC
  ISP, Buslogic and Adaptec 2940s and 3940 cards).  If your card is not
  included, it may be that the driver is not stable enough on an Alpha
  system yet.  Again, the latest MILO images are worth trying.  You can
  tell which SCSI devices a MILO image has built into it by using the
  "show" command.

  10.  Acknowledgements.

  I would like to thank:

  ·  Eric Rasmussen and Eilleen Samberg the authors of the PALcode,

  ·  Jim Paradis for the keyboard driver and the original MILO
     interface,

  ·  Jay Estabrook for his help and bugfixes,

  ·  David Mosberger-Tang for the freeware BIOS emulation and his
     support and encouragement,

  ·  Last (and not least) Linus Torvalds for the timer code and his
     kernel.

  There are a number of things that still need doing to MILO, if you
  want to add something yourself, then do let me know
  david.rusling@reo.mts.dec.com <mailto:david.rusling@reo.mts.dec.com>
  so that we do not duplicate our efforts.

  Finally, a big thank you to Digital for producing such a wonderful
  chip (and paying me to do this).

