Cyrix or motherboard issue ?

[alexino2]

Hello,

I just tested my 486 Cyrix on a 4DPS motherboard and was surprised by 2 of them :


and


The DX2-66 works only at 2x25Mhz, while 3 others brothers work at 2x33Mhz

The DX2-80 works only at 2x25Mhz and 2x33Mhz, while his brother (with no Heatsink) work at 2x40Mhz

All the rest of my cyrix work fine at their frenquecies on same motheboard.

So, Is it possible that my motherboard doesn't like them or they are fake ?



Thanks

[cuttingedgecs]

Either are possible, but the other reason is simply that they are old and wearing out. These chips, due to their age and process size are all undergoing dielectric breakdown to some degree. It will effect some more than others due to how hot these chips ran, and for how many hours during their service life, as well as the purity of the chemicals they were produced with (which will vary between fabs, chemical sources and individual chips). So this is why some chips may be wearing out faster than your others.

[Mr.Scott]

Unless you're overclocking or over volting, it's pretty hard to degrade a CPU.
They almost never go bad naturally.

[cuttingedgecs]

Back in the late 90s we frequently had to underclock Cyrix 6x86s which could no longer operate at their marked speed - even when they were only a year or so old. Intel CPUs of that period didn't seem to suffer that problem, and I can't comment on the nature and reliability of Cyrix 486s, but I've seen CPUs much younger than these go bad naturally.

[H3nrik V!]

So it seems that the Cyrix's were overclocked and/or overvolted from the factory?

[alexino2]

Thanks for answer, it's a pretty strange and interesting story !

I didn't know that a cpu could degrade with time, like a CD lol

[misace]

Which voltage did you use for them? Both are 5V pieces.

[alexino2]

[misace]

Cx486DX2-v66GP has 3,3-4V
Cx486DX2-66GP has 5V

https://en.wikipedia.org/wiki/Cyrix_Cx486

[alexino2]

[debs3759]

[alexino2]

Thanks Debs, i confirm, I tested them at 5V, they work fine.

I understand now why lower voltage Cyrix indicate 3.45V and V66

I'm new here, hope you won't blame me :p

[Mr.Scott]

Knew they weren't bad.

[debs3759]

[CPUShack]