dionb wrote on 2021-07-19, 22:46:

My Compaq SW400 motherboard (dual slot 1 with i840 Rambus chipset) from a Compaq AP550 workstation is giving me grief. […]
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My Compaq SW400 motherboard (dual slot 1 with i840 Rambus chipset) from a Compaq AP550 workstation is giving me grief.

Now, normally in that situation I stick in my POST card and look at its readout. However Compaq is special, and outputs to port 84h, not 80h - but my card picks up something regardless. Problem is figuring out what it means...

- after touching pretty much any internal hardware, it will refuse to boot, giving a 4E code. Jiggling around everything around CPU slot and (non-ATX proprietary) power connectors eventually gets it booting. After that it's rock solid and boots OK every time. Still wonder what 4E is, exactly.
- my three cA2 stepping SL3H6 P3-600E run fine (after aforementioned jiggling), but this board should support up to at least P3-1000EB after BIOS update which I have performed. I don't have one of those, but I do have a cC0 stepping SL4BV P3-866EB. It starts POST but then hangs on the splash screen with a 2C code. Would love to know why.

The latest ROMPaq (v3.05 / 686J4 ROM from 21 May 01) only just added microcode support for cB0 steppings so I guess cC0 is a no-go (my SL47S run without issue on this revision)

As far as the error codes go, maybe you could try the bootable diagnostics test / inspect diskette

ftp://ftp.hp.com/pub/softpaq/sp16001-16500/sp16085.txt

ftp://ftp.hp.com/pub/softpaq/sp16001-16500/sp16085.exe

PC Hoarder Patrol wrote on 2021-07-20, 09:19:

The latest ROMPaq (v3.05 / 686J4 ROM from 21 May 01) only just added microcode support for cB0 steppings so I guess cC0 is a no- […]
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dionb wrote on 2021-07-19, 22:46:

My Compaq SW400 motherboard (dual slot 1 with i840 Rambus chipset) from a Compaq AP550 workstation is giving me grief. […]
Show full quote

My Compaq SW400 motherboard (dual slot 1 with i840 Rambus chipset) from a Compaq AP550 workstation is giving me grief.

Now, normally in that situation I stick in my POST card and look at its readout. However Compaq is special, and outputs to port 84h, not 80h - but my card picks up something regardless. Problem is figuring out what it means...

- after touching pretty much any internal hardware, it will refuse to boot, giving a 4E code. Jiggling around everything around CPU slot and (non-ATX proprietary) power connectors eventually gets it booting. After that it's rock solid and boots OK every time. Still wonder what 4E is, exactly.
- my three cA2 stepping SL3H6 P3-600E run fine (after aforementioned jiggling), but this board should support up to at least P3-1000EB after BIOS update which I have performed. I don't have one of those, but I do have a cC0 stepping SL4BV P3-866EB. It starts POST but then hangs on the splash screen with a 2C code. Would love to know why.

The latest ROMPaq (v3.05 / 686J4 ROM from 21 May 01) only just added microcode support for cB0 steppings so I guess cC0 is a no-go (my SL47S run without issue on this revision)

As far as the error codes go, maybe you could try the bootable diagnostics test / inspect diskette

ftp://ftp.hp.com/pub/softpaq/sp16001-16500/sp16085.txt

ftp://ftp.hp.com/pub/softpaq/sp16001-16500/sp16085.exe

Thing is, this board is known to not just accept later stepping Coppermines but Tualatins too (despite "unknown CPU" error):
Re: Tualatin chipset competition pt. II

So I suspect this isn't a BIOS incompatibility as such, but something else that's fundamentally wrong - probably related to power delivery, which would explain why 600MHz works and 866MHz or above doesn't.