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CPU Overclocking

Trish's Escape from Hardware Hell Help Board » Hardware » Motherboard / CPU Related » CPU Overclocking « Previous Next »

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Posted on Thursday, November 25, 1999 - 6:25 pm:   

Hey anyone here who's crazy enough to overclock his/her CPU for increased performance? I need to know something. Since Intel CPU's are multiplier locked (you can't change their speeds by changing the CPU-multiplier settings unless you can figure out which pin on the CPU does the lock and putting some tape on it) the only way to change their speeds is by changing the speed of the Front Side Bus. Celerons and the older PentiumII's normally run with the FSB at 66MHz while the faster PII's and the PIII's use the 100MHz FSB.

I recently got a Celeron 400 for my ASUS P2B-F motherboard and made a dare to overclock it as fast as possible (after observing from a lot of hardcore gamers who also overclock their CPU's). I found that it could go up to 500MHz if I set the FSB to 83MHz and didn't have problems with my system so far (my system wouldn't boot if I set the FSB to 100MHz and try to force the Celeron to run at 600MHz). I learned however that doing so sets the PCI bus and IDE clocks to 41MHz (they normally operate at 33MHz if the FSB is 66MHz or 100MHz), and one guy from Microsoft warns that the 83MHz FSB setting can fry some PCI expansion cards and burn IDE hard drives. So to "play it safe" I went for a slightly slower setting of 75MHz on the FSB, which no one seems to be conscenred about with the PCI bus running at 37MHz, and now my Celeron runs at 450MHz. Has anyone here tried the 83MHz FSB setting on their PC's for long periods of time?
Posted on Saturday, November 27, 1999 - 4:08 am:   

I don't think there is much of a risk of frying expansion cards or hard drives unless you've got some really ancient stuff; i.e., sub 200 MB drives or ISA VGA video cards. The real question is the
stability of your system. If the overclock produces lockups or screen artifacts, it may well
be caused by one of your pci/isa bus devices that is the weak link in the chain. And the cost of replacing them with newer, more overclock friendly
devices can easily exceed the cost of getting a faster processor. My overclocking rule of thumb is
20% (in your case 480Mhz) is almost always stable, 25% (500) is pushing the limit, and anything over that is counterproductive, taking into account the
cost of replacing components, additional cooling,
and your time. This seems to apply whether you are
working with a 486sx25 or the latest board/processor. By this rule, overclocking your
PCI bus up to 40 falls into the "safe" zone, overclocking it to 41 is creeping into the "pushing the limit" zone. As for your ISA bus, there is often a divisor in the cmos settings that allows you to set it to a fraction of your PCI bus speed. The standard ISA bus speed is 8.33 Mhz. Better yet, try and eliminate those old devices altogether if you are interested in squeezing every last bit of performance out of your system.
For more on this, see:
Posted on Sunday, November 28, 1999 - 10:35 am:   

Okay, while I was running at 500MHz (83MHz FSB/41MHz PCI) nothing was going wrong or out of the ordinary on my system, aside from the intro screen of Quake3 Demo Test having distorted sound. Otherwise no crashes, no hangups, no weird stuff on screen; nothing that would be cause for alarm.

Just about all devices in my system are quite new (I have no ISA devices). Boards include a Soundblaster Live! Value board and a 3Dfx Voodoo3 3000. All hard drives are IDE UDMA type (2 Maxtor and 1 Quantum) and my CDROM drive is a Creativelabs 32x (bundled with a Soundblaster AWE 64).
Posted on Sunday, January 2, 2000 - 10:05 am:   

--If this is any help, I've been running my Celery 300A at 374Mhz for about 8 months straight (using the 83Mhz FSB setting). It never crashes ("never" for a windows box), and I've never had a failing PCI card or HD. For your reference, my PCI slots host the following:

Matrox Millenium II - 4mb
Diamond Monster 3D II
Dimaond Monster 3D II (for SLI)
Sound Blaster 128 PCI
Netgear FA310TX 10/100 NIC

I'm using a Seagate 9GB UDMA33 HD.

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