BIOS meltdown

Here’s a dilemma:
I have an Emachine with an ECS L7VMM mobo w/Athlon 1600 CPU. The D686 Phoenix BIOS chip is burned, fried, cooked. I replaced the board w/ECS KM400-M2 which, after installing drivers and updating Windows did THE SAME THING. Same BIOS too.
I’ve checked the power supply before and since and tests good. Could the CPU cause the problem? Is this a Phoenix BIOS flaw?
I’ve never come across this problem before and I’m scared to try another board. Anyone seen this before?