Front Side Bus Question

[beach2nd]

I was comparing my 3d mark scores to scores of people with similar systems and I noticed that the ones who did better than me had their FSB set higher. Mine is currnetly at 100, but most other people's were at 133. So my question is what exactly does the FSB do? How do I change it and is thier any danger in changing it? Thanks for any help, BTW my specs are:

PIII 800
Tyan Trinity S1854
512 MB pc133 (crucial)
Radeon 8500 LE (128MB) (driver ver 6.13.10.6118)
Win XP Pro

Also any recomendations or tweaks to speed up my system would be apprecaited Thanks.

 

[AndyHui]

To put it simply, the FSB is the speed at which information passes between the CPU and the chipset.

As you can see from the 3DMark results, increasing the FSB increases overall system performance.

However, processor speeds are set in multiples of the FSB, so increasing the FSB without a corresponding decrease in the multiplier will result in a processor that is running outside of its default specifications, known as overclocking.

Most other system component speeds are linked to the FSB as well, and are usually some ratio to the FSB. These include the memory speed (RAM), the PCI bus and the AGP bus.

There are motherboards now that de-link the FSB with the RAM, PCI and AGP to assist in overclocking.

Overclocking can be a very interesting pursuit, and I suggest you do a lot of reading around www.AnandTech.com or these forums.

 

[smp]

ie in your case your FSB is 100 and your clock multiplier is 8

8 x 100 = 800
which is the speed of your processor.
Your PCI bus (cards, hard drive etc) run at 33 mhz, which is arrived at by dividing the FSB by three in your case.
A system with a 133 mhz FSB has a 1/4 diviser for the PCI bus.
Your AGP bus runs at 66 mhz (am I right?) which is 2/3 of your FSB
A system with a 133 mhz FSB has a 1/2 divisor for the AGP (I could be wrong on the AGP speed though, but for the sake of example)
When you increase the FSB (which can be done either using jumpers on the motherboard or in the bios depending on your motherboard, some not at all) you are increasing all of the other bus speeds, which can cause system instability.... unless you go from 100 to 133 and if your board has the appropriate PCI/AGP divisors to keep those busses running at their normal speed. You really only want to make your RAM and processor go faster. So, running at an FSB of something like 112 probably isn't the best idea, as you'll be running your PCI and AGP out of spec, and even though a lot of devices can handle the higher frequency, it creates more opportunities for instability.