This Intel 486dx4-100 Overdrive CPU has a high CPU benchmark score and standard AMD 5x86-p75-133.

Speedsys benchmark scores:
Intel Overdrive 486dx4-100 score = 38
Standard AMD 5x86-P75-133 score = 50

Errr...I think you're misreading your own benchmarks. The Intel gets 38, and the AMD 50.

However, keep in mind that these are synthetic benchmarks. Speedsys is notoriously inaccurate for measuring older CPUs. Try comparing using something like DOOM. It's already been discussed somewhat, but I think it's been accepted that the Intel DX4 is just about the same speed as an AMD DX5-133. This is apparently because intel made some enhancements to the ALU and FPU in their DX4, whereas AMD just slapped on some extra cache.

Okay, referencing other benchmark scores this Intel Overdrive CPU scored 3 points higher than a standard 486dx4-100.

Standard Intel 486dx-25 score = 9
Standard Intel 486dx-33 score = 12
Original Intel 486dx2-50 score = 18.1
Standard Intel 486dx2-66 score = 18.6
Intel 486dx4-75 = 29
Standard Intel 486dx4-100 score = 35
Intel Overdrive 486dx4-100 score = 38
Standard AMD 5x86-P75-133 score = 50
AMD 5x86-P75-133 @ 166mhz = 60

The score not only depends on the CPU itself but other things (chipset, RAM), see the "Ultimate 486 Benchmark Comparison" thread: an Intel DX4-100 WB scores 42. My own DX4-100 in WB mode scores almost that much.

I bet if you compare a standard DX4 in WT with the overdrive version using the same motherboard and RAM you would get pretty much the same score.

Doornkaat wrote:

Two ideas:
Many of those are proprietary form factors. Maybe the CPU would not physically fitin the case because of the large heatsink or it would collide with long expansion cards?
Or is it possible that those boards simply would not support AMD CPUs? I've had motherboards that would not run an AM486DX2 with i486DX2 settings.

Well, Some bad news. The AMD 5x86 CPU did not work. I tried several jumper setting and dip switch setting and
I could not get it to work with my IBM PS/1.
The Instructions read that it is NOT compatible too.

But these did work:
Intel 486sx-25 ( Bus speed 25mhz ) Standard CPU
Intel 486dx-33 ( bus speed 33mhz ) Standard CPU
Intel 486dx2-50 ( Original CPU ) ( 2 x 33mhz )
Intel Overdrive CPU 486dx4-100 ( 33mhz bus )

Did you try the 5x86 in 3x mode?

Anonymous Coward wrote:

Did you try the 5x86 in 3x mode?

Yes, I tried all the DIP switch settings too.
I will have to find a compatible motherboard to test.