overclocking maths :)

[LaRnZ1]

how do you work out what your cpu speed should be at a certain fsb?

i have a p3 500e @ 150 fsb which = 750 Mhz so am i right in sayin that 150 fsb is 50% of the base cpu speed again?

just wondering if i purchase a p3 733 133mhz coppermine if i clock that to 150fsb will it reach a gig? as it will only be a 17% fsb increasement?

cheers guys.. im kinda new to this

 

[bacillus]

cpu speed = fsb x multiplier!

 

[Dark4ng3l]

5.5*150=825

You will never reach anything near 1 gig with a 733

 

[Hanpan]

NO. Your cpy runs at multiplyer times fsb.

A 733 has a 5.5 multiplyer. So at 150x5.5 (150 fsb) you are running 825

A gig would need a fsb of 182. Realistically not gonna happen.

 

[Verygreedy]

It depends on what your multiplier is set at. For me, I run a 100FSB (which is actually 200) but 100x a 12x multiplier.. for 1200 mhz. For me this is not overclocked since its a genuine 1.2 ghz cpu. If I had a 110 fsb (actually 220 since the FSB is automatically x2 ,not to confuse you ) but 110 x12 multiplier I would be at 1,320 mhz.

You generally have to UP the voltage a bit to get these higher speeds. My old 450 K6-2 was running at 105fsb x 5 multiplier.. =525 mhz. Make sure you get your voltage setting right and you have good venilation and cooling for the high overclocks..

 

[LaRnZ1]

arhhh ok np they also sell a 700E thats standard clock is 100Mhz so whats the multiplier on this chip how do you know what it is? one of these should make a gig considering tis a 50% fsb rise eh?

I WANT A GIG DAMMIT!!! hehe just not enuff spondoolies to actuly get a gig chip their like $800 bucks in new zealand

 

[Verygreedy]

You wont hit a 1ghz with a 700.. not very likely at all.

 

[Pakman]

I believe LarnZ1 is a bit confused. In order to find your processor speed. Like in your last post a 700E P3. You would multiply the front side bus times the multiplier. For the 700E P3 chip, the front side bus is 100mhz and the multiplier is 7. This is the default for that particular processor and will vary from processor to processor. So, 100 X 7 = 700mhz. Now let's say you wanted to run that processor at 1000mhz or 1Ghz. You would have to increase the front side bus to 143. So 143 X 7 = roughly 1000mhz.

 

[Rand]

Verygreedy, remember the guy is talking INTEL, not Athlon. So your comments of 100MHz FSB=200MHz data rate etc isnt valid for a P3.

The Processor clockspeed is the FSB times the processor multiplier.
So for a P3 733EB it is 133MHz FSB x 5.5.
For a 700E it is 100MHz FSB x7.

To get the clock multipler of any CPU just divide the core clock speed by the FSB speed and it'll come out with what the multiplier would be.

 

[Verygreedy]

yes..I was talking for me.. his FSB is 100. Intel mult. is locked correct?? so he wont be able to OC much at all.

 

[smp]

I'm a AMD man myself, if you can, go with AMD, if you already bought a motherboard for a PIII, then I think you need a 700 w/ 100fsb. If I am not mistaken, the 700 is 7 x 100. If you can get the FSB up to 133, you will get 931 (7 x 133). I heard that if you want to overclock a pentium III, you should get the 100 fsb ones, cause they have some headroom, whereas the 133's don't. I also heard that there is no reason for the 100 fsb chips not to hit 133 fsb, unless it can't handle the clock.. try the cpu processors and overclocking forum.. lot's of ppl in there will be able to help you out.
Now back to pushing AMD on ppl .. With an Athlon chip, the multiplier is locked, just like the PIII's, but this is reversable (whereas on the PIII's it's not!). On the Athlons you can unlock the multiplier simply by connecting (shorting out) the L1 bridges on the chip. Then you can play with the multiplier all you want. AMD's processors are on par or greater in performance than anything Intel can offer and significantly less expensive.
I don't know what your situation is regarding what kind of hardware you already have (ie, motherboard).. but if you're looking for a new system, let me be the first to recommend an AMD system.
<edit> AMD chips have a DDR (double data rate) fsb. This means that AMD's 100 mhz fsb is actually 200mhz.. and the newer AMD's with 133 ddr fsb are actually 266, you'll hear ppl say both, but they are the same thing, effectively 266 mhz!!! Now my analogy of this is breathing in and out at the same time, much more air, for less breaths per second, dig?) </edit>

 

[thermite88]

<< AMD's with 133 ddr fsb are actually 266 >>

So, if I get an AMD 1.2 GHz Thunderbird with a 9.0 multiplier, I am actually running at 9.0x266 FSB = 2.4 GHz. Wow, who needs overclocking with this new math.

 

[Budman]

thermite88,

266 is actually a 133 double pumped in amd.
so 9x133=1200

 

[Verygreedy]

I think he knew that.. hopefully.

 

[Budman]

It's hard to tell without the Sarcasm smileys.

 

[Verygreedy]

heheh :disgust:

 

[thermite88]

<< 266 is actually a 133 double pumped in amd. >>

So 266 is actually 133. Help, I can't understand this new Math.

Does double pumped mean times two?

So 1200x2 = 2400.

Hum, I still come up with 2.4 GHz.

 

[Budman]

thermite88,

Amd can transfer on the rising edge &amp; falling edge,so that's why it acts as if it were running at 266,but in reality it's really running at 133mhz,it only performs like it would be running at 266mhz.

I am sure other can explain it much better than I can.

 

[thermite88]

Budman,

I am familiar with the Double Data Rate archetect and it application in memory. The FSB (front side bus) clock is a function of the motherboard dependent on the clock generator and BIOS setting. When the MB clock generator generates one hundred thirty-three million cycles per second, it is called a 133 MHz FSB. The clock does not change whether the data is read once or twice. AMD tried to redefine FSB frequency in the spirit of the Cyrix &quot;Performance Rating&quot; clock.

It fools the technically uneducated, but a clock cycle is a clock cycle. You cannot change that. I am just having a little fun at smp's expenses.

There are two facts:

(1) The DDR memory is not limited to AMD. VIA has a chip set for using DDR memory with Pentium 3 processor.

(2) In benchmark test, the DDR showed no advantage over SDRAM in office suite bench and showed a 10% increase in performance in 3-D gaming.

To call a 133 FSB &quot;266&quot; is totally nonsense.

The DDR memory does have a higher bandwidth than current PC-133. The DDR price is about double that of PC-133, but the performance is not.

 

[smp]

hey! Who's talking about memory? Are you arguing that AMD's processors don't infact operate at DDR fsb? I don't know, by reading these forums all the damn time, I would have thought otherwise.
<edit> AMD chips operate at 100 and 133 fsb, but it's ddr, in and out, so the transfer rate is doubled. It's still 133 clock cycles, just in and out for every clock cycle, I don't understand what you're arguing, and why you need to have fun at

<< my expense >>

?
You're point there was what?</edit>

 

[Jiggz]

ANYWAY! Going back to the original thread of LarnZ1, you were absolutely right on your first example in determining the FSB and subsequently the multiplier for your CPU. But every CPU design have its limitation. Just because you were able to achieve a 50% overclocking on a P3-500 that doesn't mean a P3-900 will achieve the same. The P-3 core is practically limited to a max of 933-966 Mhz. The original P-III (.25 micron) was about 550-600 Mhz. You see if you buy a P3-700 the most you can overclock it is maybe within the range of 933-966 assuming all systems are go especially the mobo and memory. Since P3 are multiplier locked sometimes you're better off buying a cheaper 600-700 Mhz and overclock it to it's max. Of course, by doing this you are also overclocking the rest of the system except maybe for the PCI (and AGP is you have 4 divider in you mobo).

 

[Pakman]

The FSB and Memory bus are 2 different buses going to the North Bridge chipset from what I understand from someone on this board.

 

[thermite88]

smp wrote:

<< Who's talking about memory? Are you arguing that AMD's processors don't infact operate at DDR fsb? >>

DDR is a memory archetect and has nothing to do with porcessors. The same processor can work with SDR or DDR memory using different motherboards.

<< I don't understand what you're arguing, and why you need to have fun at my expense. >>

I saw that you have no understanding of what you are talking. It is good nature fun to correct a misconception. Here is some direct quote from Anandtech's VIA KT-133A Review

<< If you want AMD 760 class performance without the added costs of migrating to DDR SDRAM, the KT133A is the perfect solution. While DDR SDRAM may have its place later on down the road when applications are more memory bandwidth intensive, or upon the release of the next-generation Athlon core (not Palomino) that is rumored to be much more like the Pentium 4 in terms of its design, it currently doesn?t make sense for the average user. >>



<< Purchasing a KT133A board and either using a new 133MHz FSB Athlon such as the 1.2GHz parts or lowering the clock multiplier of an older 100MHz FSB part and using the 133MHz setting to get increased performance without actually overclocking your CPU would be your best bet for use with the KT133A. >>



<< You saw the performance advantage that a 1GHz Athlon gained by simply lowering its clock multiplier from 10.0x to 7.5x and using the 133MHz FSB support of the KT133A. You can guarantee that an even more aggressive overclock would result in even better performance figures. >>



<< For the current KT133 owner, it doesn?t really make too much sense to go out and get a KT133A board, but if you?re looking to build a new system then the KT133A is definitely the way to go. >>



<< From a manufacturing standpoint, it doesn't really cost any extra for the KT133A to be used instead of the KT133. The chips should cost the same, leaving the only extra costs associated with a KT133A board up to the ability of motherboard to be reliable at the 133MHz FSB which shouldn't be too hard for most manufacturers. >>



<< It looks like although VIA was late to the game with a DDR SDRAM chipset for the Athlon, they do get the last laugh as the KT133A offers 95 ? 100% of the performance of the AMD 760 without the added cost of DDR SDRAM. >>

 

[thorin]

&quot;arhhh ok np they also sell a 700E thats standard clock is 100Mhz so whats the multiplier on this chip how do you know what it is? one of these should make a gig considering tis a 50% fsb rise eh?&quot;

FSB x Multiplier = CPU Speed

Therefore:

CPU Spd / FSB = Multiplier
700MHz / 100MHz = 7

7 x 150MHz = 1050MHz = Good Luck!

Thorin