Can't get Cyrix 5x86-100GP to clock to 100mhz

[RWallmow]

I am trying to get my Cyrix 5x86-100GP CPU to clock to the full 100mhz, but thus far I have failed. I can get it to clock to 52mhz (per syschk) at 25mhz bus, and 69mhz (again per syschk) on a 33mhz bus, both times syschk reports the CPU is using 4x multiplier (which makes no sense at a 4x it should be running at 100 or 133).

I am using a "trinity works" "power stacker" voltage regulator adapter (with some DIP switches to control multiplier and cache). I have tried their automatic setting and their 4x write-through, and 4x write-back settings all with the same effect, either 52 or 69mhz depending on system boards 25/33 bus setting. My next attempts will be to try the 3x multiplier options and see what happens.

I should also note that its NOT stable at 33 bus setting, so when running at 69mhz it crashes a lot (not in DOS running syschk, but BSODs a lot in NT).

I can't run it without the power stacker, the socket is 5-volt and the CPU is 3-volt, I know it should boot, but that cant be good to over-volt a CPU for very long, which is why I bought the power stacker adapter.

for some background the system board is a Compaq Presario CDTV-520, only CPU options on board are 25/33 bus setting and SX/DX setting.

 

[DrSwizz]

I was experimenting with a Cyrix 5x86-100GP about two weeks ago and "syschk" gave me strange clock speed readings too. I suggest you try a different utility to determine the CPU slockspeed.

 

[RWallmow]

I was experimenting with a Cyrix 5x86-100GP about two weeks ago and "syschk" gave me strange clock speed readings too. I suggest you try a different utility to determine the CPU slockspeed.

I will have to try that, you have any other you suggest, I have been using syschk for decades?

 

[DrSwizz]

Perhaps chkcpu32 will work correctly?

 

[RWallmow]

Perhaps chkcpu32 will work correctly?

CHKCPU sees it at 100mhz, while SYSCHK reports 52mhz, so I am guessing its just syschk reporting wrong, would explain why its unstable at 69Mhz (by syschks mark, was probably probably really clocking to 133mhz).

 

[twolazy]

Have you tried turning off the cpu cache yet? I know some earlier 486 motherboards had incompatibilities with on-die cpu cache of dx2/dx4/overdrive/586 cpus.

 

[RWallmow]

Have you tried turning off the cpu cache yet? I know some earlier 486 motherboards had incompatibilities with on-die cpu cache of dx2/dx4/overdrive/586 cpus.

I have tried all the cache settings no stability issues related to cache, CPU is supposed to clock at 100mhz, so its no wonder its unstable at 133. My problem all along I guess was syschk doesn't work right with this system/cpu.