[Etherboot-developers] Re: [RFC] Relocation techniques...

[<pjc...@el...>]

I'm not sure if this precisely fits in with the relocation being discussed
here, but it foiled my efforts to etherboot from my existing network 
cards.

I've got one of the 3com 3C905B-NM cards, for which 
disklessworkstations.com sells proms.  These are the cards that overload 
the MII signal to choose which ROM bank to read.  The current (hack) 
solution is to use a boot disk which locks the MII setting on.  That way 
the card can see more than 4KB of the boot rom, and load the etherboot
code into memory.

However, this is rather sloppy.  It leaves the one signal stuck on.  
Always.  Even when you don't boot from the bootrom.  Linux handles this 
situation just fine.  However, DOS TCP stacks pitch a fit.  This makes our 
Ghost boot disks fail, rendering the machines rather useless.

Apparently the right solution is to have a small piece of code which lives 
in the low 4KB of the ROM.  It switches the banks, copies the ROM into RAM 
somewhere, and switches back.  Then it boots.

All that to say, if you're toying with relocation and other such memory 
constraints, please consider building the little low-memory shim into your 
plans.

	-P