Helo guys, please can somebody help me to identify this motherboard? AB-PM4..... It's Abit PM4???? Can't find any informations about this motherboard, also any jumper settings. I tried many jumper settings, but seems like mobo doesn't support X5 processor. Many thanks guys!
Going by this https://theretroweb.com/motherboard/manual/35089.pdf
It seems you have to rotate the jumper caps on J18 90 degrees and go across to get volts to the CPU.for everything else try settings for AMD DX4
Edit: nope, got the pin numbering tangled in my thinker.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
Hi barry07,
This Abit AB-PM4 looks like a great board for the Am5x86-P75. However, finding the correct jumper settings and a BIOS that supports this CPU will be a challenge. 😉
The manual at https://theretroweb.com/motherboards/s/abit-a … .-1.0#downloads for the practically identical AB-PM4T board looks usable for your PM4.
I also see a 09/04/95-SiS-496-497/A/B-2A4IBA13C-0C BIOS on this Retroweb page. Is this the BIOS you are running?
Looking at the AB-PM4T manual, for the Am5x86 I would start with the P24D jumper setting for the CPU Type Configuration:
RN6: not installed
RN10: 1-8
RN14: 1-8
RN16: 1-8
RN17: not installed
JP13: open
JP24: 1-2
JP32: open
The CPU Speed Configuration can remain at 40MHz:
JP12: open
JP14: closed
The CPU Voltage Configuration should be set at 3.45V for the Am5x86, exactly as is show on your motherboard picture (red jumpers):
JP18: 3-5 and 4-6 closed
JP19: open
JP20: closed
JP21: open
JP22: open
With these settings and the 09/04/95-SiS-496-497/A/B-2A4IBA13C-0C BIOS, the Am5x86-133 should be detected as an Enhanced Am486DX4-120 and run correctly at 3 x 40 MHz and L1 cache WB mode.
Please let us know if this works.
However, this BIOS doesn’t support the Am5x86-P75 in x4 multiplier mode, so a BIOS update is needed to get the CPU up to a 4 x 33MHz or 4 x 40MHz speed.
Jan
barry07 wrote on 2023-02-17, 19:18:mobo doesn't support X5 processor
It most likely doesn't, the 486-133 was released in November 1995 which is a couple months later than the latest bios version known.
Your best bet is running it as a DX4-100 with 16KB cache (enhanced Am486).
You could also dump the bios rom to see if it is a different one.
