Overclocking fsb question

[peter p]

I've done some overclocking on the PIII's and was reading some posts on overclocking the P4's. I'm a little confused when I see something like "2.8 at 250 fsb" running at 3.5".
Shouldn't that be running at 70000 mgz. (2800 x 250 fsb =7000).

Thanks

[mtb856]

It's the multiplier for the P4 - 18 for example- X the FSB speed

So, its 250 X 18 = 3500

[oc_newbee]

Originally posted by mtb856
It's the multiplier for the P4 - 18 for example- X the FSB speed

So, its 250 X 18 = 3500

250 x 18 will be more like 4500

[peter p]

Mabe I didn't make myself clear.
I see on this site that someone has a p4 2.8 at 250 fsb running at 3500. If you do the math 2800 x 250 fsb, the cpu should be running at 7000mgz not 3500. It's all over this site with guys running 250 fsb but the speed is half of what it should be. Am I missing something here?

[NinjaWreck]

Originally posted by peter p
Mabe I didn't make myself clear.
I see on this site that someone has a p4 2.8 at 250 fsb running at 3500. If you do the math 2800 x 250 fsb, the cpu should be running at 7000mgz not 3500. It's all over this site with guys running 250 fsb but the speed is half of what it should be. Am I missing something here?

Yes you are. Here are the specs for a stock 2.8 (2800mhz) processor that has not been overclocked:

2800mhz
200fsb (adjustable)
14x multiplier (locked)

The first number is your stock rated speed of the processor: 2800mhz. The second number is your front side bus speed 200mhz. The third is your multiplier which is used to calculate your processors frequency by being multiplied by the fronst side bus (fsb). So here is a little equation:

14 X 200 = 2800

When you overclock the adjustable fsb to say 250mhz, then you can increase the overall frequency of your processor. Here would be an example of that equation:

14 X 250 = 3500

You can shorten all this up by saying:

(Stock) 2.8 @ 250fsb = 3.5 (overclocked)

[peter p]

I put a computer together for a friend. It was a celeron 2.4 with an asus p4p800s mobo. I went into the bios and switched the cpu frequency to manual and raised the fsb to 133. When it posted it said the computer is running at 3.2 ghz and the memory was at 333 fron 266. Is this right or do I have to start at over 200 fsb to overclock?

Thanks

[NinjaWreck]

Originally posted by peter p
I put a computer together for a friend. It was a celeron 2.4 with an asus p4p800s mobo. I went into the bios and switched the cpu frequency to manual and raised the fsb to 133. When it posted it said the computer is running at 3.2 ghz and the memory was at 333 fron 266. Is this right or do I have to start at over 200 fsb to overclock?

Thanks

You do not have to reach 200fsb to overclock. We are just discussing the newest pentium 4's fsb speeds. Older ones have lower fsb, like the Celeron you are talking about.

Celeron 2.4 specs:

2400mhz (400fsb, quad pumped 100mhz)
100fsb
24 X

Equation for that chjps frequency would be:

24 X 100 = 2400

You overclocked your fsb to 133 so that it would look like this:

24 X 133 = 3200mhz (3192)

So you effectively overclocked that chip from a less expensve 2.4 400 fsb chip to a 3.2 533 fsb (quad pumped 133) chip

As soon as you increase the fsb of a motherboard then you are overclocking the chip. New pentiums have a range of fsb settings. They are as follows:

100mhz (400fsb)
133mhz (533fsb)
200mhz (800fsb)