It's likely that your 486DX processor includes system management mode (Intel: "&E" marking) or even write-back caching (Intel: "&EW" marking). These processors make use of signals not used on older processors, so they are more picky about getting the jumpering correct. The web page from The Retro Web you linked doesn't include any jumper setting guides, though. A prime candidate for a problem is the CLKMUL jumper that is intended to choose between 3x clock and 2x clock on the 486DX4 processor: 2x is "jumper not installed" and 3x is "jumper at 1-2" on many mainboards, whereas "jumper at 2-3" is reserved. That setting was originally intended by Intel to request a multiplier of 2.5, but this setting doesn't work with most 486DX4 processors and causes them to not run at all.

I have other same model motherboard and everything works fine (same settings) . I got the idea to i installed another cpu TI486dx2 66MHz but 3.3V and it works 😀 ....Now I don't understand anything . Cpu 5V works , 3.3V works 33MHz and 66MHz but 100MHz not .

Ok ..Now works Intel 486dx 100Mhz but setup is for IBM dx100MHz .

Thx mkarcher