Reply 40 of 44, by Beerfloat
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jakethompson1 wrote on Yesterday, 03:47:Unfortunately, between D3 and D4 a ton is going on. This is where the BIOS turns on the RAM, initializes the chipset, and switch […]
Beerfloat wrote on Yesterday, 02:09:Any chance this kind of replacing K6-problematic instructions with NOPs and adjusting the checksum would work on something like the G7-ZG AMI BIOS for the TMC PCI54PV?
It boots with Pentium MMX but both K6-2 and K6-3 on Evergreen and Powerleap interposers just hang (with BIOS POST card code D2D3).
Unfortunately, between D3 and D4 a ton is going on. This is where the BIOS turns on the RAM, initializes the chipset, and switches to executing the BIOS from shadow RAM rather than ROM. The compressed portion at 5000h also appears to be something that amideco can't handle (but since you don't see D4, I'm not sure it ever executes anyway). There are a few 0f 30s in the uncompressed part, but they look like false positives and not actual wrmsr instructions. So it's difficult without knowing where it gets stuck. Rather than straightforward like Award, perhaps something in the CPU detection code was set and doesn't break right away, only causing failure between D3 and D4.
edit: there is MHz detection code between D3 and D4. Perhaps it runs too fast and there is overflow or divide by zero--you could experiment with as slow bus speed and multiplier as possible.Beerfloat wrote on Yesterday, 02:09:Same question for the Spring Circle SF586 VIP3A-ZS1 AWARD 4.50PG BIOS, really.
I am less concerned about CPU detection and setting all registers correctly than about simply getting it to boot. Can always run k6init after.
That one is quite similar to jheronimus' one.
At offset 17F3Eh there is 0F 30 (wrmsr). Change it to 90 90 (nop nop) and I expect you'd have to change the checksum at 1FFFFh to 22h.
Really appreciate the quick and thorough response jakethompson1. I will be trying that on the SF586 BIOS.
With the original checksum at 1FFFFh looking like F7h, and you saying new checksum likely 22h, let me see if my small brain can figure out how these checksums work!
