P5G-MX CPU support unlock

[-=blAck=-]

I just wanted to use this old Asus P5G-MX board as a testbench, but faced one problem - it boots only with conroe CPUs.
All others (I tried Celeron 331 and P4 640) shows this screen and turns of after few seconds:


Okay, I thought that is microcode-related. So taken microcodes from P5GC-VM PRO BIOS from asus site (that supports all what I need), added some LGA771 microcodes (remember, this is a testbench, so I like it support as much CPUs as possible), updated all CPUID+Platform to the latest binaries, shrinked splashscreen to full black to fith all that microcodes to 512k image, made it, flashed it - and no changes, it still doesn't want to run with Cel-331 and P4-640. I think there is hardcoded CPUID check. Can somebody help me to override it? I'm not so experienced in ASM coding

Error string and its ID in AMIbcp: http://i.imgur.com/In56Wpj.png

Bios image I have for now:
http://rgho.st/private/89tnCpr8p/6a9a86f...5e51b4845f

Yes, I understand that board have weak power source to run all CPUs, but I just want it to start and boot, load will depend on what CPU I will use.
And if something goes wrong - I have hardware programmer to reflash its BIOS. So I'm free to experiment with it.