The divisor of OCing

[Garfield]

I don't understand it. People talking about not exceding 1/4. What is this all about? Thanks...

--Garfield

[Jon]

The most common frequency for PCI devices is 33MHz. Being on a bus speed that commonly runs anywhere from 66MHz, 100MHz to 133MHz, a divisor set by the clock generator is needed to keep it in spec.

A system running a 133MHz bus speed needs a 1/4 divisor for the PCI bus to be 33MHz. 133/4=33. So on so forth for other bus speeds.

USB and AGP also have their own divisors.

This is the simplest explanation I could come up with.

[RainMaQer]

Originally posted by Jon
The most common frequency for PCI devices is 33MHz. Being on a bus speed that commonly runs anywhere from 66MHz, 100MHz to 133MHz, a divisor set by the clock generator is needed to keep it in spec.

A system running a 133MHz bus speed needs a 1/4 divisor for the PCI bus to be 33MHz. 133/4=33. So on so forth for other bus speeds.

USB and AGP also have their own divisors.

This is the simplest explanation I could come up with.

And done very well;)
And to go a little further... Network cards and some sound cards really don't like it when the pci bus is out of spec... they usually have a little lead way... but in my case an fsb of 140 with a 1/4 divider gives me a pci bus speed of 35... my network card doesn't like it very much... sometimes it'll work sometimes it won't:beer: ALSO your ide channels for your hard drives and cdroms is bound by the pci divider... too high of a pci bus speed and they may fail or create errors as well.;)

[Yodums]

Your HDD will not like high PCI Bus as they run on it too so it'll start corrupting files.

[Garfield]

So, when you OC, what "number" raises that you can't go over the 1/4 divisor?

[Shadow ÒÓ]

raising the FSB raises the mhz for the pci and all.

To raise the FSB from say your 133 memory/processor to 140, instead of the PCI being at 33 mhz with a 1/4 devider, it would be at around 37 mhz. (140 / 4) there are also boards that have 1/5 deviders and 1/6 I believe.

[RainMaQer]

Examples:
FSB is set to 100 with 1/3 divider= PCI bus@33(within spec)
FSB is set to 133 with 1/4 divider= PCI bus@33(within spec)
Now... FSB set to 110 with 1/3 divider= PCI bus@36(out of spec)
FSBXmultiplier=Processor speed.... 100X7=700 mhz processor. 110X7=770 mhz processor.

[Garfield]

So, when you raise the FSB, you are "fooling" the comp to make the processor and the PCI's run faster, therefore OCing your comp. But, you can't go over the divisor, right? I don't understand that. What can't you go over? What speed?

[Garfield]

Originally posted by RainMaQer
Examples:
FSB is set to 100 with 1/3 divider= PCI bus@33(within spec)
FSB is set to 133 with 1/4 divider= PCI bus@33(within spec)
Now... FSB set to 110 with 1/3 divider= PCI bus@36(out of spec)
FSBXmultiplier=Processor speed.... 100X7=700 mhz processor. 110X7=770 mhz processor.

Where did you come up with the multiplier, '7'? And, my previous question, what can't you "go over"? Thanks...

[Jon]

The only way you can go over a divisor is to go on to the next one. If there isn't a next one, then the frequencies for all peripheral devices just keep going further and further out of spec.

The clock generator and chipset itself of the motherboard must support higher divisors in order to keep the PCI, AGP, etc withing it's specified frequencies.

It's all hardwired into the circuitry...including the divisor.

[Garfield]

When you say "go onto the next one", you just keep going up from 7, to 8, to 9? And then how do you know when to stop? And, how do you set the multiplier?

[RainMaQer]

My Typical Intel Overclock:
Raise the FSB from default of 100MHz to about 105MHz. Check temps and stability.
Raise from 105MHz to the next setting (110 i think). And again check the temps and stability.
Keep doing this until the temps are too high or the system becomes unstable then back down a notch.
On my motherboard the pci dividers are set automaticaly. Upto 89 Mhz there is a 1/2 divider, 89-124 there is a 1/4 divider, and any higher there is the 1/4 divider. It's not tricking the computer... it's forcing it. It's not the divider you can't go over. It's the MHz you can't go over... due to temp or stability.

*edit* I got the 7x multiplier out of the air... mine is 7.5... some are 8,9,10,11,12... depends on the default speed of the processor.

[Yodums]

Rain basically explained it to you..

Its simple to overclock, really just complex in other ways but really easy to understand.

I'll try to do my own version so you can just read both and may get a better understanding of either;

You should worry about dividers unless your on a 83fsb which has a 1/2 divider and 160fsb+...

Your PCI devices should take anything between like 31-38 fine anything above it will cause your HDD to run strange or PCI cards crapping out but NIC's like 3com really take the big spikes :)

Heres what to expect from PCI dividers under these fsb settings:

66 - 75 = 1/2 PCI is basically in spec
83 = Chances are taken 15-25% your HDD will corrupt files
100 - 105 - 110 - 112 - 115 = 1/3 Spec is in place
120 1/3 = 40, chances are 10% something will happen
124 = Possible 1/3 or 1/4 if you have an option definitely go 1/4
133 and above is 1/4

Then take Rain's procedure of testing the fsb and stuff with stress tests and MONITOR YOUR TEMPERATURES.

[plague]

Originally posted by Garfield
When you say "go onto the next one", you just keep going up from 7, to 8, to 9? And then how do you know when to stop? And, how do you set the multiplier?
I think youre getting a little mixed up between divisors and multipliers.
the '7' that Rain referred to is the multiplier. It is used to get the total cpu speed (multiplier x FSB = cpu speed).
the PCI divisor is automatically set by the mobo. the normal speed of the PCI is 33 mhz. therefore for the PCI to run at 33 mhz, it needs to run at 1/4 of the FSB speed if FSB is 133 mhz. However, when you increase the FSB, you also increase the PCI bus as stated in previous posts. when you say "you cant go over the divisor", I think youre a little confused. theres nothing really to "go over." what you are going over is the default PCI bus speed of 33 mhz when you increase the FSB. and you can "go over" it....thats what "over"clocking is all about:D

[RainMaQer]

Sorry I should have waited to through the multipliers in there:beer:

Garfield... I HIGHLY recommend you read this (http://www.overclockers.com/tips120/index06.asp)
I don't mean this as an insult to you in ANY way... I've read and even gone back to read it again...VERY informative..:D

[Garfield]

Okay, I'll give it a look, fellas, and then I'll probably be back with more questions. But, just another quick one. You have an exact divisor and you can't change that or it doesn't change? Thanks, all!

[Garfield]

Okay, so I have a 366mhz celeron (:rolleyes: ) with a 66mhz bus speed, so my multiplier would be around 5.5, right? Is this how you find the multiplier?

[RainMaQer]

Yep... that makes up the processor speed... sooo... at an fsb of 66 your divider (current) is 1/2. This should change or can be changed along with higher fsb.

[Garfield]

Originally posted by RainMaQer
Yep... that makes up the processor speed... sooo... at an fsb of 66 your divider (current) is 1/2. This should change or can be changed along with higher fsb.

Wait a minute, I don't understand what you are saying here. Your divisor can be found by dividing your original processor speed by the bus speed, right? So, where did you get 1/2?

[RainMaQer]

The divider is in relation to the pci,agp,etc... the multiplier is in relation to the processor... divide FSB to get pci and stuff and multiply FSB to get processor speed.

[Shadow ÒÓ]

I was gonna try and help....but I'm not sure how. Read that beginners guide as suggested......some of the explanations here can be confusing if not elaborate enough.

[Garfield]

Okay, so the higher you raise the FSB, the higher the denominator of the divisor goes, right? So, as you raise the FSB, the divisor automatically changes? Thanks, RainMaQer, I really appreciate this becuase I am absolutely new to this OCing. Sorry for the confusion.

[RainMaQer]

Some change automaticaly and some require you to change it manually... Like mine for instance... the fsb can be changed from 66 to 150... but the dividers are designated to change ONLY at certain fsb settings... 1/4 only kicks in at 124... 1/3 kicks in at 89....

[Garfield]

Oh, so as you raise your FSB, there will be a certain FSB setting in which your divisor will change automatically. That's neat. So the IDE ports are on the PCI then, right (just a side question because I know that HDDs hook up to the IDE ports)?

[RainMaQer]

Yes the ide channels run at whatever speed the pci bus runs at... 33 MHz when within spec... but not ALL motherboards select the divider automaticly... some require this setting to be changed manually... either in the bios the same way as the fsb or by changing the position of dip switches or jumpers...

[Garfield]

So, what is commonly known as "bus speed" is really the FSB?

Okay, thanks for all of this information. It is much appreciated!!! :D

[RainMaQer]

More or less... yes... there's FSB= Front Side Bus, PCI Bus, AGP Bus (not sure on that one), ISA Bus (again not sure)

[Garfield]

Thanks again, friends!

[Yodums]

The divisor will expand through higher FSB's but FSB's usually have a direct divisor check my last thread on this post.

Lets say your on a 66fsb your divider is 1/2 no matter what since it is a perfect spec and to find out PCI bus you take 66 divided by 2 since its the divider.

If its 133 wit a divider of 4 then you take 133 divided by 4(Easy grade 4 math!)..

Why are you worrying about dividers so much the FSB's have automatic settings you should just be worried if your on 83 bus, 120bus, 160+ bus.

So FSB divided by divider is the PCI BUS.

The AGP Bus is what bus your AGP port runs on(Accelerated Graphics Port, slot your video card goes in)... Usually 2/3 or 1/2 of the FSB. So 100fsb would run on a 66 AGP bus if set on 2/3. To find the AGP bus of 100fsb and your AGP bus was 2/3, take the fsb divided by the 2/(3) - I forgot whats it called again think it was divisor anyways.

100/3 = 33

Then times it by the number infront of the 3 which is 2 in this case thus the AGP bus runs on 66 fsb.

Yodums

[Garfield]

Do you have to worry about the AGP bus like the PCI bus, too?

[RainMaQer]

Not as much if you have a descent vid card... my agp is WAY out of spec and my GF3 handles it like a champ...

[Garfield]

Okay, I'll have to invest in a good video card then. I was thinking a GeForce3 (I don't know, maybe ASUS or something). Definitely something to handle the OCing.

[Yodums]

Not really no even old video cards will do good at AGP bus speeds till like 105.

If your board has a 1/2 AGPbus divider thats even better since its near spec at times.

[plague]

Garfield, you're worrying way too much about this. Unless youre going to run your fsb up beyond 160, I'd say youll have no problems if you have decent hardware. And some people have theirs way above that without problems.

[Garfield]

So, does the multiplier also change when you overclock? For instance, my multiplier is ~5.5 (366 mhz/66 FSB), and then when I would OC it, the FSB would raise. So, if I raise it to, say, 70, then I would be running at:

70 x 5.5 = 385mhz

But, will this multiplier remain constant? Or will it rise/fall?

[RainMaQer]

With OLDER intel processors and just about all AMD processors the multiplier can be changed... it's done manually in the bios... when upping the fsb it does not change automaticly. By older intel I mean before the pentium 2.

[Garfield]

So, by changing the multiplier, that is how you make the CPU go faster? So two things (raising the FSB and raising the multiplier) contribute to the "speeding up" of the computer?

[RainMaQer]

Yep... if your unconfortable with overclocking the whole system... via FSB... you can (if able) change the multiplier and overclock JUST the processor.OR you can go "No Holds Bard" and raise the FSB AND the multiplier.

[Garfield]

I think I understand, RainMaQer. Yeah, I'm pretty sure I'm understanding this. Thanks!

[Yodums]

No you multiplier doesn't change as Intel multipliers are locked from the early P2 233 don't bother changing them.

Yodums

[Garfield]

Originally posted by Yodums
No you multiplier doesn't change as Intel multipliers are locked from the early P2 233 don't bother changing them.

Yodums

Well, I'm going to build an AMD based system. So, I won't have to worry about the lock.

Garfield

[Yodums]

Originally posted by Garfield


Well, I'm going to build an AMD based system. So, I won't have to worry about the lock.

Garfield

If its an XP series you will have to order an unlocking kit and connect the bridges carefully.

[res0r9lm]

Originally posted by RainMaQer
Some change automaticaly and some require you to change it manually... Like mine for instance... the fsb can be changed from 66 to 150... but the dividers are designated to change ONLY at certain fsb settings... 1/4 only kicks in at 124... 1/3 kicks in at 89....
mine changes at 120

[Garfield]

Originally posted by Yodums


If its an XP series you will have to order an unlocking kit and connect the bridges carefully.


Really? Is this hard and/or risky? Do you suggest another route?

[res0r9lm]

Originally posted by Garfield



Really? Is this hard and/or risky? Do you suggest another route?
no other way other than overclocking by fsb alone or getting a t bird

[Garfield]

How much does this kit cost?

[res0r9lm]

$15 or 20

[Garfield]

Okay, thanks!

[Garfield]

Another question...

When you say, "my computer is pc66" (which mine really is), are you referring to the speed of the FSB?

Another thing (slightly off topic), but I was looking at RAM and I saw PC133 RAM, and then I saw PC2100. Isn't that a really really long jump with the speed?

Garfield

[RainMaQer]

The pc133 is sdram... for pentium systems primarily... the pc2100 is DDR (double data rate)... for AMD systems and also for the newer version of the Pentium 4... the 2100 means 2.1 GBs bandwidth.... the 133 stands for 133 FSB... usually about 400MBs bandwidth.

[res0r9lm]

Originally posted by Garfield
Another question...

When you say, "my computer is pc66" (which mine really is), are you referring to the speed of the FSB?

Another thing (slightly off topic), but I was looking at RAM and I saw PC133 RAM, and then I saw PC2100. Isn't that a really really long jump with the speed?

Garfield pc 66 is sdram for 66mhz, pc 100 is 100 mhz, and so on. pc 2100 is ddr ram for 133 mhz

[Placid]

Originally posted by res0r9lm

no other way other than overclocking by fsb alone or getting a t bird

The mp cpu is the xp counterpart and comes factory unlocked.
The price is around $70 more for the same speed as a xp but if you add the $20 for the unlock kit plus the risk of ending up with a dead cpu it might be worth it for some.

[res0r9lm]

Originally posted by Placid


The mp cpu is the xp counterpart and comes factory unlocked.
The price is around $70 more for the same speed as a xp but if you add the $20 for the unlock kit plus the risk of ending up with a dead cpu it might be worth it for some.
the mp might have came unlocked at one time but the last one I seen was locked but didn't have the pits looked kinda like this : don't know if they are all going to be like that or not

[Placid]

New's to me.
Did you actually see this cpu in a motherboard and verify it was locked?
The bridges will appear open on the surface that is normal as the bridges connect below the surface. That is why the pits are created when the lazer cuts thru the surface and the bridges below on xp cpu's.

[res0r9lm]

Originally posted by Placid
New's to me.
Did you actually see this cpu in a motherboard and verify it was locked?
The bridges will appear open on the surface that is normal as the bridges connect below the surface. That is why the pits are created when the lazer cuts thru the surface and the bridges below on xp cpu's.
ok that makes sense. wonder if mp would clock further than xp

[Garfield]

How, exactly, do you unlock the XP?

[res0r9lm]

Originally posted by Garfield
How, exactly, do you unlock the XP?

http://www.overclockers.com/tips693/

[Garfield]

Thanks but it seems to be a bad page. "Page cannot be displayed".

Garfield

[res0r9lm]

ok try again

[Garfield]

Wow! When I read that article, my jaw dropped! That looks really hard!!!! And, if you go over hardly anybit, then you ruin a $130 CPU!!!

Is it as hard as it looks? That tooth-pick was mighty small...

Garfield

[res0r9lm]

can't be as hard as it looks... too many people are unlocking successful

[Garfield]

It's so...small!

[res0r9lm]

t bird brides are even smaller

[Garfield]

Hmmm...so it's not a real "kit", per say. You have to buy supplies that aren't really made for unlocking, they just work. Sounds really risky with a $150 CPU. But, if that's what I need to do to OC, then that's what I'm going to do!!!

Garfield

[res0r9lm]

best buy right now is xp 1700+ $112 on pricewatch

http://www.pricewatch.com/1/3/4105-1.htm

[Garfield]

What is "Palimino"?

[res0r9lm]

xp

[Garfield]

Well, on the page you gave me, there seems to also be an XP with the same features (at least the brief features they supply on the description) except the one says "Palimino". There must be a difference between the normal XP and the XP Palimino, right?

Garfield

[res0r9lm]

Originally posted by Garfield
Well, on the page you gave me, there seems to also be an XP with the same features (at least the brief features they supply on the description) except the one says "Palimino". There must be a difference between the normal XP and the XP Palimino, right?

Garfield
nope, same chip. palmino is another name for xp.

[Garfield]

Originally posted by res0r9lm

nope, same chip. palmino is another name for xp.

But then why are they advertising it twice?

[res0r9lm]

pricewatch is a site that searches for best prices on computer gear on the net. each column is a different site

[Garfield]

Okay, thanks!

[res0r9lm]

welcome

[Garfield]

Originally posted by Yodums
Not really no even old video cards will do good at AGP bus speeds till like 105.

If your board has a 1/2 AGPbus divider thats even better since its near spec at times.

So, when you raise the FSB, do you also OC the AGP bus when you do this? This confuses me. Is FSB all of the buses (PCI, AGP, the CPU -- which bus is the CPU on?)? Is it the bus?

Garfield

[Maddman]

every mother board has a chip on it that act's as a clock. it controls the clock cycles on the board. the FSB is usualy set to a 1:1 ratio on this clock. The other buses are then set off of the FSB/clock at varing ratios to keep them in spec with the standard by witch they are governed. PCI standard is 33mhz AGP is 66mhz ect. When you raise the speed of the FSB you are also rasing the speed of the clock chip and all of the busses dependant on the clock/FSB. Some bios manufactures have built in to their bioses a feature that lets you alter the divisor of some of the busses that are clock/fsb dependant so you can keep it in or close to spec. If they do not then you will have to live with overclocking everything attached to the bus in question and some hardware doesn't like to do this. Also the clock chip sometimes doesn't like to be pushed either and that is when you reach the maximum FSB that a MB will overclock to.

[RainMaQer]

Originally posted by Garfield


So, when you raise the FSB, do you also OC the AGP bus when you do this? This confuses me. Is FSB all of the buses (PCI, AGP, the CPU -- which bus is the CPU on?)? Is it the bus?

Garfield

The FSB is the main bus that is tied into all components of the motherboard. The cpu has a multiplier for its speed and PCI/AGP have dividers to make their speed. But all dividing and multiplying starts with the FSB (Front Side Bus).

[Garfield]

Yes, that's what I thought. So, when you OC the FSB, you are raising everything. Or, you can choose to raise separate devices.

Is there one divisor for the system? Or are there different divisors that you have to change for each device to keep them in spec? Thanks! :D

Garfield

[RainMaQer]

There's one divider for the pci bus (pci slots, ide, etc.) and one for the apg (vid card) that I know of.

[Maddman]

every bus has a diferent one pci,agp,isa. Different MBs have different settings for this and some have no user changable settings at all. This is why chousing a mother board is so important.

[Garfield]

Originally posted by Maddman
every bus has a diferent one pci,agp,isa. Different MBs have different settings for this and some have no user changable settings at all. This is why chousing a mother board is so important.

Okay, thanks RainMaQer and Maddman, I understand now. BTW, I'm going with the Epox 8KHA+...

Garfield