I am having problems with my Gigabyte GA-486vs motherboard.
http://www.motherboards.org/files/manuals/47/486vs8a.pdf

It has always given me problems with 486dx4 CPU’s.
It works fine with a 486dx-50 5v CPU but not with a 486dx4-100 CPU.
I have been able to get it to work once before with the 486dx4-100 but only for a while
And then it stopped working.

I have the motherboard setup on a test bench with a NEW AT 300watt power supply
And Cirrus Logic 5429 VLB graphics card. And just a keyboard.
Nothing else.

I tried all the possible jumper settings. I can’t get it to post with the 486dx4-100 3.3v
I tried several tested known good 486dx4 CPU’s but none will posts.

What could be wrong ?
Works fine with a 486dx-50 CPU.
Motherboard is functional and working.