Hello everyone, I am on a project to install a VRM by Necroware on a Siemens Nixdorf System Board D943 motherboard (the PC itself is a Siemens Nixdorf Scenix C5 Pro). You can see documentation on the retro web: https://theretroweb.com/motherboards/s/siemen … board-d943#docs.

Motherboard has VIO and VCore joint together along 3.3V rail. I could remove the union between VCore with 3.3v, and VCore with VIO by removing 4 0 hms resistors inside the socket and another 2 0 ohms resistors pretty close to the socket. But found no way to isolate VIO from the 3.3 rail. Anyway I built the VRM and tried to tested with a Pentium 200 MMX. PC doesnt post. After some testing I found out that VIO drops to 0 volts once you power on the PC with CPU socketed on, meanwhile VCORE stays stable at 2.8v.

I also contacted Necroware on this Github topic, you can check the entire story there.

I am pretty lost right now, don't know what is wrong with the motherboard. I would thank any help. Thanks in advance.