If it's not that connector then must be the extra cable of the PSU leading to some sensor, anyway flashing the bios most likely will fix it. I'll give the board to my associate (he has a programmer) but most likely he will keep it.

P5S-VM owner here, mine came from an HP Pavilion as well, can confirm 100% it uses a normal ATX power connector and it should power on without needing anything else attached.

Here's mine:
http://theretroweb.com/hardware/motherboards/hp-asus-p5s-vm

Thanks but do you use the HP bios?
Also i tried connecting the cpu fan to the PS_FAN connector and it didn't turn just a brief attempt.

dondiego wrote on 2021-10-22, 09:39:

If it's not that connector then must be the extra cable of the PSU leading to some sensor, anyway flashing the bios most likely will fix it. I'll give the board to my associate (he has a programmer) but most likely he will keep it.

Alright, why not to try, the BIOS is socketed so there nothing to lose. What would be great is to dump it or download it from the HP FTP and compare the data with the retail one with a BIOS editor and an hexadecimal editor to check the differences. If someone have time to lose...
Anyway, please let us know if flashing the retail BIOS changed anything, thank you.

I've joined the discord and computerguy08 is using the ASUS bios. I've downloaded the HP bios from somewhere but i don't think it's worth comparing.
I'll ask my associate he's a electronic technician i'm just a computer one.

My "partner" came today and programmed the bios with the one from the asus page and it doesn't boot, the file is "p9vm1005.awd". Same as before, the fan spins when i press the power button and nothing else. It hangs and i need to keep the button pressed to turn it off, no beeps without ram. Seems something is "flashing" between the atx connector and the cpu. R25 is missing but i found another pic on the web and it's the same.

The p5s-vm is an exclusive hp board and it's a clone of the asus p5-99vm, that one has an extra bios revision on the asus web.
The boards are different, besides the resistor (someone said in discord the asus board has it) and the undocumented PS_FAN connector capacitors are in different positions.
Some p5-99vm boards have the right name on the pcb and it has asus written on it, others have a label on top of p5s-vm. But they are different.
Mine is revision 1.01 of the board and unless i'm wrong it doesn't work with an standard psu, may be later revisions do.
I think that connector doesn't give power to the fan and it's a tachometer, i could try to connect something there to fool the board but i don't know how.
The bios is not the problem, both are interchangeable i think. @computerguy08 what revision is yours?

Just wanted to reply in case anyone is searching for this answer....

I have an Asus p5s-vm Rev 1.01. In order to get it to boot and power on at all, it needed a fresh cmos battery AND some type of disk hooked to primary IDE (along with a floppy drive).

Once i did that, I was able to flash it with the bios on the Asus web page (which was the p5-99vm bios, ver 1006). The board now boots and posts as such and has no other problems.

It's not a "crap" board. It's not a P2B, but the caps are all good and otherwise has the quality that all Asus boards from that time frame have (which is to say, very good).

This is not the first Asus board i've run across that's needed a good cmos battery and/or something hooked to primary ide in order to show some life when powering on.