First post, by topaz75
I am building a 486 machine and am running into some issues.
Board is a PC Chips M912 V1.7. It came with a AMD 486 DX2-80 CPU which runs fine. I tried to upgrade to a AMD 486 DX4-120 and set the jumpers according to the documentation found here: http://www.elhvb.com/mobokive/Archive/Oldman. … ips/jumpers.htm
I tried both alternatives mentioned on there for AMD 486DX4, my chip is the later V8B variant. In both cases, the system boots, but only runs the CPU at 100 MHz. When I am using the settings for the V8B version, it gets to the POST screen where it displays the 100 MHz, and then hangs when the separate IDE controller tries to access the HDD.
Any ideas what to try next? SInce the CPU is a 40 MHz FSB variant, I find it odd that the 80 MHz one works fine, and the 120 MHz one that really is identical except for the internal clock multiplier won't work.