====== Daniel Verkamp: COMBOOT Support ======

===== Notes =====

==== COMBOOT ====

  * http://syslinux.zytor.com/wiki/index.php/Comboot_API
  * What should happen if/when a COMBOOT executable returns?  Do any other image types ever return?

=== Basic COMBOOT execution sequence ===

  * Detect image type (.com/.cbt -> 16-bit COMBOOT; .c32 or magic number B8 FF 4C CD 21 -> COM32) - case-insensitive filenames?

== 16-bit COMBOOT ==

  - Copy image to offset 0x100 of some segment
  - Set up PSP in same segment
  - Set up IDT entries to point at COMBOOT API implementation (stubs in lowmem to call actual protected-mode implementation?)
  - Change to real mode
  - Set segment registers CS = DS = ES = SS to segment containing PSP and code
  - Set SP to 0xfffe (end of 64k segment)
  - Near call 0x100 (start executing)

== COM32 ==

  - Copy image to virtual address 0x101000
  - Set DS = ES = SS to the same base as CS (flat address space)
  - Set FS = GS = 0
  - Set ESP to end of available memory
  - Allocate bounce buffer in lowmem
  - Push args onto stack (helper functions, bounce buffer, other args from user)
  - Call entry point

==== Development and Testing Environment ====

=== QEMU ===

New option in QEMU 0.9.1:

''-bootp file     advertise file in BOOTP replies''

Example command (modified contrib/bochs/qemu.sh):

''qemu -net nic,model=rtl8139 -net user -boot a -fda ../../src/bin/rtl8139.pdsk -bootp http://server/file.gpxe''

This way there is no need for TFTP or DHCP servers when testing in QEMU.

=== Real Hardware ===

Development machines:

  * "sequoia", Pentium 4 2.40 GHz, 1 GB RAM (Gentoo Linux)
  * "maple", Athlon X2 4200+, 2 GB RAM (Windows Vista Ultimate 32-bit)

Server machine (DHCP, HTTP, TFTP, etc.):

  * "pine", Pentium III 1.0 GHz, 256 MB RAM (Gentoo Linux)

"Guinea pig" machines:

  * "tulip", Athlon XP 2100+, 768 MB RAM
  * "spruce", Pentium II, 256 MB RAM
  * Pentium 133 MHz, 16 MB RAM

Network cards (PCI):

  * 3Com 3C905-TX (3C905-B)
  * Linksys LNE100TX (DEC 21140 based)
  * SMC EtherPower 10/100 9332DST (DEC 21140 based)
  * HP J2585B 10/100vg (not supported by Etherboot/gPXE; ancient :-) )