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Can't understand FSB

post #1 of 9
Thread Starter 
I'm new to the overclocking game and have searched, and read, and googled, and read those googled searched things, and i just cant get a good grasp on how the numbers are related.

i have googled and forum searched "understanding fsb", "FSB relationship to cpu", and various other terms. i cannot find the info i need. i would appreciate help, links and explainations, and dumbing down. if you dont have anything to contribute please move along.

i am running a core 2 duo e8500, evga 780i mobo, corsair gs600 psu, 9800gtx with 512mb and 8gigs of ddr2 (i forget the speed, whatever was the highest a few years back) memory. from what i understand, clock speed is a product of FSB and the multiplier, which would be 333 x 9.5 to give 3.16 ghz. peachy. but i go into the bios and 333 is nowhere to be seen. fsb is now listed as 1333... which is rated FSB? so i'm supposed to change the rated FSB, or use the number i want to try and multiply by 4, and use that?

i want to aim for a final clock speed around 3.6-3.9. if the multiplier is 9.5, and if i understand properly, then i want a fsb speed of 378-410. but i've also read that you cant just set this number as you please, it has to be specific, otherwise everything goes to hell. but the BIOS has a setting to link the FSB to the memory... so then the problem is solved?


i also dont fully understand reaching a stable clock. first i read FSB has to be a specific number and then i read to increase by increments of 10? so in my case an effective 95mhz increase? and bumping voltages after the system becomes unstable? so if the computer doesnt boot i have to get into the case and dial the settings back? is that what software overclocking saves time with, finding instable speeds?


very very confused. this is ALOT of info and i'd very much like to just try and understand and get some basic numbers to play with. if that was at all confusing to read, you can only imagine where i am now
i've read faqs on tom's, this site, hexus.... i've tried and i'd like help, this is what a forum is for. help is appreciated but if you're just going to post a link, an explaination to go along is the only way thats helpful. i've read plenty but i just dont understand it.
post #2 of 9
FSB = Front Side Bus

Also, read this.
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post #3 of 9
Quote:
Originally Posted by Wiremaster View Post
FSB = Front Side Bus

Also, read this.
I'd echo his response. Before you worry about overclocking, I'd suggest waiting until you get a better grasp on how data moves throughout the system. It is rather daunting at first - but don't give up; you'd be surprised how much information you're retaining as you trudge through things.

I know it seems silly to link this, but wikipedia has a very broken-down version of how what the system architecture looks like in the era of the FSB. I wouldn't be able to explain it any clearer than it is worded there.

Edit: also, read your motherboard's manual. Like, six or eight times. Trust me.
Edited by Aeschylus - 4/20/11 at 11:23pm
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post #4 of 9
For some reason, NVIDIA decided that overclocking with the nForce chipset means that you play with the Rated FSB. The Rated FSB is the result of multiplying the FSB by 4 (it's QDR, or "Quad Data Rate"). With Intel's chipset (meaning, not the NVIDIA but Intel), overclocking is done by playing with the FSB instead of the Rated FSB.

Now, all overclocking should be done in the BIOS and never with software. Ever. Always, always, always do all of your overclocking in the BIOS. This is extremely important.

If I remember correctly, NVIDIA made it easy by displaying the CPU clock speed in the BIOS as you adjust the Rated FSB so that you don't have to do any math. However, if you still want to do the math then here is the formula when working with the Rated FSB:

Rated FSB ÷ 4 x the multiplier.

So if the multiplier is 9 and if the Rated FSB is 1333, then the formula is 1333 ÷ 4 x 9. Although, I'm fairly certain that it's not necessary to do this math while you're adjusting the clock in the BIOS as I think it shows you what the CPU clock will be.

Again, never use software for overclocking. In fact, if you have any overclocking software installed of any kind, then uninstall it now because it will always apply its settings when Windows starts.

Regarding setting a specific FSB clock vs. going up in increments of like 10 MHz: you can actually do whatever you want. Overclocking basically turns you into a scientist, so it is always about experimentation, trial and error. Some people prefer to shoot straight to their desired overclock and then work from there while others prefer to slowly increase in steps of like 10-20 MHz. There really is no right or wrong way.

Regarding "FSB Memory Clock Mode" where you get the option to Unlink them or Link them (and whatever else is available), I recommend using "Unlinked" because this actually makes overclocking in the nForce 780i chipset a bit easier. What this actually does is it makes it seem like the FSB clock and the Memory Clock are no longer linked when in reality you're just working with dozens of additional ratios (or "dividers"). So you're much less limited. Experiment with it though because you will notice that the FSB clock and Memory clock are still linked; you will find that the Memory clocks you can select are still determined by the FSB clock you're using.

Finally: what do you mean by "so if the computer doesnt boot i have to get into the case and dial the settings back?" Did someone cause you to think that you have to open the case to make changes? If so, then rest assured that this is not true. However, if you meant "get into the BIOS", then nevermind.


Anyway, overclocking really isn't as big of a deal as some people make it seem. However, it does require loads and loads of patience as well as a positive attitude (because it's actually fun), and it's also very rewarding.

Oh, I almost forgot about the voltages: that's all about experimentation too. However, stay below 1.45V for the core voltage as it is displayed by CPU-Z (not as it's displayed in the BIOS), and keep the FSB Voltage/Termination no higher than 1.4V because I think this voltage goes through the CPU.

Speaking of voltages, nForce boards are rather notorious for needing to use relatively high voltages. So to achieve a solid 1.0 GHz overclock (4.16 GHz), you may even need 1.4V for the FSB Voltage, and you may even need like 1.34V as displayed by CPU-Z while under full load. However, don't use that right away because it's still all a matter of experimentation!
Edited by TwoCables - 4/20/11 at 11:33pm
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post #5 of 9
Thread Starter 
thank-you muchly for that, two cables. very helpful.

yes, i did mean if all goes to hell and wont go into BIOS. something about a jumper, i read, is necessary to reset to factory and thus enable BIOS again. and the troubleshooting list for that was rather long.

i have read that FAQ/guide and the mobo manual countless times. that one post clears alot up. i dont get along with math, so its good to know i can just experiment.

i guess then, i will go ahead and set that FSB, start with cpu and other voltages bumped up some.

the only thing to ask then, is for a general voltage to shoot for. i'd like to just shoot for 3.8 ghz to start with, is 1.25 a good ballpark?

also, if i just set a high voltage (like that 1.34) and work down, can too low a voltage prevent me from entering the BIOS?

and lastly, i wonder about software overclocks as being useful. from what i read, they allow you to play around with numbers until you reach instability, and then use those numbers in the BIOS without fear of not being able to get back in; then you just delete the utility. is this a bad idea?

any more opinions or insight is very much appreciated. there is a wealth of knowledge but it relies on the reader to have alot of prior knowledge!
post #6 of 9
Get used to moving your clear CMOS jumper. If you set something really unstable, it might not boot so you will need to clear it. It's really easy to do. It will be a 3 pin thing like this:



You just move the jumper to the other 2 pins, let it sit for a couple seconds, and then move the jumper back to the original spot.

I do not recommend setting higher voltage and working down, then you have no idea what kind of voltage you need to be stable. If you start low and work your way up you will have a better idea. Voltage needed will depend on the CPU stepping, is it E0 or C0? CPU-Z will tell you.
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post #7 of 9
Quote:
Originally Posted by 7even62 View Post
thank-you muchly for that, two cables. very helpful.
You're welcome!


Quote:
Originally Posted by 7even62 View Post
yes, i did mean if all goes to hell and wont go into BIOS. something about a jumper, i read, is necessary to reset to factory and thus enable BIOS again. and the troubleshooting list for that was rather long.
Regarding the jumper as it specifically relates to the 780i, it works like this: turn the system off, move the jumper to the other pins and then turn the system on. It really is as simple as that. If you ever need to do it again, then repeat the process, but of course you'll be moving the jumper back to the other 2 pins. I had an nForce 680i SLI board, and this is how it worked for me.


Quote:
Originally Posted by 7even62 View Post
i have read that FAQ/guide and the mobo manual countless times. that one post clears alot up. i dont get along with math, so its good to know i can just experiment.

i guess then, i will go ahead and set that FSB, start with cpu and other voltages bumped up some.

the only thing to ask then, is for a general voltage to shoot for. i'd like to just shoot for 3.8 ghz to start with, is 1.25 a good ballpark?
I suppose so. However I'm concerned about cooling (I forgot to ask): what are you using for CPU cooling?


Quote:
Originally Posted by 7even62 View Post
also, if i just set a high voltage (like that 1.34) and work down, can too low a voltage prevent me from entering the BIOS?
Sure! I mean, it's just one of many things that can make the board unable to perform the POST (the Power-On Self Test). So this is when you would turn the system off, move that jumper over, and then turn the system back on (you don't have to move it back before turning the system on).


Quote:
Originally Posted by 7even62 View Post
and lastly, i wonder about software overclocks as being useful. from what i read, they allow you to play around with numbers until you reach instability, and then use those numbers in the BIOS without fear of not being able to get back in; then you just delete the utility. is this a bad idea?
I don't know, however I have never known any experienced overclocker who trusts software for overclocking.


Quote:
Originally Posted by 7even62 View Post
any more opinions or insight is very much appreciated. there is a wealth of knowledge but it relies on the reader to have alot of prior knowledge!
Or it relies on the writer to share their prior knowledge. hehe
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It's a computer!
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post #8 of 9
Thread Starter 
i'm cooled by a thermalright ultra 120 extreme, with a scythe high flow (cant remember which, highest cfm i could find locally) blowing on it. case is an antec 900, all the fans turned up and a fan in every hole, i even think i have a tiny factory fan on the northbridge. noise is no issue for me, i have an air filter in my room that is far far louder than the pc, and i use headphones usually. in cpu-z it says i have a stepping of 6, revision c0. i doubt i'm reading that right.

max temp is 74 for this cpu, so i'll guess that anything below 70 is acceptable and shoot for high 60's as a max?

just about ready to tear into this %$#@.

hope this doesnt get too tedious!
post #9 of 9
Quote:
Originally Posted by 7even62 View Post
i'm cooled by a thermalright ultra 120 extreme, with a scythe high flow (cant remember which, highest cfm i could find locally) blowing on it. case is an antec 900, all the fans turned up and a fan in every hole, i even think i have a tiny factory fan on the northbridge. noise is no issue for me, i have an air filter in my room that is far far louder than the pc, and i use headphones usually. in cpu-z it says i have a stepping of 6, revision c0. i doubt i'm reading that right.

max temp is 74 for this cpu, so i'll guess that anything below 70 is acceptable and shoot for high 60's as a max?

just about ready to tear into this %$#@.

hope this doesnt get too tedious!
You're reading CPU-Z correctly. It's just that they reversed them for some reason and still haven't changed it, so you have a C0.

Anyway, 72.4°C is actually not the maximum safe temperature. It's not even related to the core temperature. This is merely the "Tcase" specification while the actual maximum safe core temperature is closer to 100°C (which is the Thermaljunction Maximum, or "Tj. Max.").

So instead, try to stay out of the 70's for the reason of trying to avoid instability as opposed to trying to avoid damage. I mean, a core temp of 75°C is still very safe even though that much heat under load could cause some instability when overclocked. Although it would be stable while at stock.
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It's a computer!
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