i have a cyrix pr200 with a rated clock speed of 166mhz(66fsb x 2.5)with the fsb overclocked to 80mhz and the multiplier set at 2x(clock speed of 160.) all of this on a MTI mustang board with the sis5571 chipset. my question is whenevr i try to switch to the multiplier to 2.5 with 80mhz bus(200mhz). my system loses stability. same thing if i use the 66mhz bus with a mulitplier of 3, i get the same thing. does anyone have any ideas about bringing up the stability at all. any suggestions would be greatly appreciated.
here's the real test
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Grizely1
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- Dec 31, 2007
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Cyrix chips absolutely suck for overclocking. When you raise the FSB or Multiplier without lowering the opposite (If you raise FSB, you lower Multiplier), you're overclocking your CPU (making it run at a higher clock speed then what was intended by the manufacturers). I doubt there's any way to bring up the stability on an old Cyrix....
I would tend to blame your mboard rather than the Cyrix chip. The SIS 5500 chipset series were notorious for their instability and general unreliability. I once upgraded a friends computer with a SIS 5598 chip based mboard made by PCchips. We originally intended this system to run an AMD K6-2 350mhz I was using this same chip in my computer at the time and knew it to be of the utmost quality and reliability. On booting the computer it would boot into DOS without any problem but as soon as any syntax was typed would lockup. We tried clocking down the AMD chip to 200mhz but it made no difference. On trying the AMD CPU in my computer and found it to work perfectly. I managed to get windows 98 to work on his computer buy connecting his hard drive into mine and installing it, (windows 98’s configuration had to be modified once back in his system of cause). Once we got 98 up and running we had a bit more stability but after a few minutes of typing in word 97 the computer would completely freeze. Luckily I had a Cyrix 233mhz chip lying around at home, which we tried in this mboard and found it fixed the problem of windows locking up but the system was still unstable in DOS. I suggested that he take the mboard back and exchange it for a better quality one but he wanted to keep it because it featured onboard video and sound. We took the AMD chip back and exchanged it for a Cyrix 333mhz which ran fine in it for about six months. By then he decided to upgrade to a AMD K6-2 500mhz with an Epox EP-MVP3G2 mboard and the system has run perfectly ever since. He gave the old mboard to me but I threw it away saying that I would not want to inflict it on anyone.
PS: The PCchips mboard had a maximum FSB of 112mhz Im not sure if yours features this being an older SIS chipset. What ever the case I think you would have better luck throwing away that mboard and getting one with a VIA chipset.
PS: The PCchips mboard had a maximum FSB of 112mhz Im not sure if yours features this being an older SIS chipset. What ever the case I think you would have better luck throwing away that mboard and getting one with a VIA chipset.
The AMD K6-2 350 chip was meant to run at a genuine 100mhz FSB. When we clocked it down we run it at 66mhz FSB but still had the same problems. The Cyrix 233 & 333 were 75mhz & 83mhz FSB respectively. I feel the fault lay with the mboard because even with the Cyrix chips we still had problems with DOS locking up. My friend didn't mind this as windows 98 worked reasonably stable and he only wanted the computer for office work. Since this saga I have tracked down others through the Internet who were unfortunate enough to have owned this particular mboard and others with the SIS 5500 series chipset. All had similar problems some even worse!!!
In the old days Tom's Hardware would only recommend overclocking Intel chips because Cyrix chips were “factory overclocked”. While the old Intel chips usually had headroom for overclocking Cyrix chips were run at very close to their maximum possible speed with no room left to OC. Also you may already know this but a Cyrix pr200 is not designed to run at 200MHz but was marketed to be as fast as an Intel 200MHz processor while running at a slower speed (166MHz). Cyrix claimed that due to a better design that 166MHz Cyrix was as fast as a 200MHz Intel chip.
I would rather have a sharp stick in the eye then run any CPU at < 200MHz. The crappiest systems you can buy today are over twice that fast. If you want a faster system why not just buy one? Complete Gigahertz AMD systems are selling without a monitor for < $800.00.
I would rather have a sharp stick in the eye then run any CPU at < 200MHz. The crappiest systems you can buy today are over twice that fast. If you want a faster system why not just buy one? Complete Gigahertz AMD systems are selling without a monitor for < $800.00.
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