PCChips M919 V3.4B/F POST Fail \ VOGONS

PCChips M919 V3.4B/F POST Fail

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First post, by cluster.fsck

Posted on 2026-02-13, 19:26

cluster.fsck Offline

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Picked up a PCChips M919 V3.4B/F board yesterday with an AMD Am5x86-P75 that fails to post. I confirmed the jumper settings are correct for this CPU before powering on. With just a know good stick of RAM and a POST card installed, the boot halts at code 0xC7. Same behavior with and without a video card. According to https://blog.theretroweb.com/2024/01/20/amibi … st/#AMI_WinBIOS, this indicates CMOS shutdown test register failure, but I know from reversing a HiFlex BIOS a few years back, there are many different lists of codes.

I read a couple posts suggesting that the state of the turbo button may cause this behavior, but placing a jumper across the turbo button pins has no effect. Moving J4 to clear CMOS and pulling the battery also didn't help. I guess I'll take the BIOS at it's word for now and try replacing the RTC. Ebay has tons of Motorola MC146818A, which looks to be a drop-in replacement for the ALi M5818 currently on the board. Anything else I should be looking at? BIOS is attached.

Reply 1 of 3, by Nexxen

Posted on 2026-02-13, 19:40

Nexxen Offline

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Tried with another 486 cpu?
Bios needs to support the cpu and usually latest will, or on theretroweb you'll find the latest patched version.
If you have a second bios chip that you can program.
https://theretroweb.com/motherboards/s/pcchips-m919-ver-3.4b

The included bios chip is most probably a otp.
At this stage I suspect the bios and not the rtc.

L2 cache is fake here.
Have you checked cpu voltage?

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Reply 2 of 3, by weedeewee

Posted on 2026-02-13, 20:21

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Was the removed battery a new good +3v one ?

also bios seems to be a slightly different version that what is available on theretroweb
https://theretroweb.com/motherboards/s/pcchip … 9-ver-3.4b#bios

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Reply 3 of 3, by cluster.fsck

Posted on 2026-02-26, 15:23

cluster.fsck Offline

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Turns out the crack in the upper left corner had severed some traces. A quick touch-up with a soldering iron brought her back to life, fake cache and all. Wish I would have noticed before removing the RTC but it required the replacements not working for me to take a closer look at the board. FWIW, the MC146818AP does not seem to be a drop-in replacement for the ALi M5818. I couldn't get the CMOS settings to stick with the Motorola chip. It would always report checksum failure, run setup utility. Re-installing the ALi chip made the problem go away.

Alright, time for some fun. Does the AMD-X5-133ADZ require a heatsink and/or fan? Everything I've read seems to indicate no, not unless you're overclocking. A cache stick design is freely available https://github.com/pancakepuppy/M919_3.3V_1MB_cachestick. Would it be possible to replace the asynchronous SRAM with pipeline burst? Finally give this board the cache it's been pretending to have all these years?

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