Trying to get iPXE working on a 486

[FozzTexx]

I'm trying to get iPXE working on a 486, but it always hangs right after loading the image from floppy. To avoid any problems with physical media I'm using a Gotek with the ipxe.dsk on it.

I found this thread from last year and disabled the TIVOLI_VMM_WORKAROUND and also enabled the debug messages as suggested. This gets the 486 to get as far as the access_highmem message and then it hangs. I have three different 486DX computers (two are genuine Intel, one is AMD) and they all hang in the same place. Oddly if I try it on qemu-system-i386 -cpu 486 it works there, so there's something that qemu isn't emulating right. If I try the ipxe.dsk on a real Pentium it will get past the access_highmem message and get as far as printing the iPXE banner and trying to configure the ethernet card.

I tried copying the libprefix.S progress macro into liba20.S and renaming any symbols used in the macro in case of conflict. When I try to make the calls to progress from within liba20.S it just hangs. My guess is the progress macro is clobbering something and unfortunately my x86 assembly experience was 30 years ago and on an IBM XT with an 8086.

I'm not quite sure what to try next to debug this further.