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Overclocking a Core2Duo E4500 on EVGA 680i SLI Motherboard


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#1
stearmandriver

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Hey guys,

I've been studying overclocking for a few days, and I think I understand the theory behind it, though I haven't tried it yet. I'm finishing setup on a system I just built, and I'd like to try overclocking this processor. I've found several excellent tutorials online that deal with overclocking core2duos on this motherboard, and they all agree except on one point. This is what I'd like some opinions on.

I'm basically planning on following this tutorial, as it seems nice and conservative in regards to heat, voltages, and FSB bumps:
http://pc.ign.com/ar...7/747606p3.html

That's page 3 of the tutorial, and it's there that this tutorial makes a popular reccomendation: unlinking the FSB and RAM settings in the BIOS before boosting FSB. However, this tutorial recommends leaving them linked:
http://www.evga.com/.../tm.asp?m=61146

I'd just blow this off and go with the conservative guide, except... what this guy is saying makes good sense to me (but I have no idea if I really understand any of this or not, hence my desire for a second opinion :) ). Here's the pertinent excerpt:

"Linked and Synced baby. In every single over-clocking guide I have seen the first thing they say to do is unlink the FSB and Ram. I strongly disagree. This was a common over-clocking practice during the P4 days of the past, when the FSB was 800Mhz and anything faster than DDR 400 was tough to come by. By today’s standards that would be 1066 and DDR2 533, are any of you running DDR2 533? I didn’t think so. Even I managed to scrounge up some DDR2 800.
So linked and synced your FSB to Ram ratio will be like this…

QDR 1066 =DDR2 533
QDR 1333 =DDR2 667
QDR 1500 =DDR2 750
QDR 1600 =DDR2 800
QDR 1800 =DDR2 900
QDR 2133 =DDR2 1066

This provides what I consider a true 1:1 FSB/Ram ratio..."


Particularly in my case, I can't figure out why I wouldn't take his advice and leave them linked. I'm using an E4500 with a QDR FSB of 800Mhz (with a multiplier of 11), and 2 gig of DDR2 800. So it seems to me that - assuming the apparently optimum ratio of 1:1 - I'd have to push the QDR FSB past 1600 Mhz in order to bump the RAM's limit of 800Mhz. With a multiplier of 11, that kind of FSB would yield a clock speed of 4.4 Ghz. I'm pretty sure that ain't gonna happen... :)

So, what do you all think? Linked and synched, or unlink and adjust the RAM speed manually? If I did unlink and just used a 1:1 ratio, wouldn't my settings be the same as what the motherboard would do automatically?

I know, this is a long question. I'd really appreciate any help or input. Thanks!
Joe
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#2
stettybet0

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I have the same mobo as you, and I link and sync my e6750. It makes sense for me to do that, since my stock FSB is 1333mhz. A small OC to 1600mhz FSB leaves my ddr2-800 RAM running at it's stock speed. My current OC to 1800mhz FSB has my CPU at a zippy 3.6ghz (stock 2.66ghz) and my RAM at 900mhz. However, since you have a much lower FSB, this wouldn't make much sense for you. 1:1 also wouldn't make much sense, as it would probably be holding your processor back, since most processors can OC higher than RAM. For instance, I can only keep my ddr2-800 RAM running stable with tight timings at 900mhz. If your RAM is similar to mine, then you could only manage a 400mhz OC of your processor while at a 1:1 ratio. For this reason, I would recommend trying a 5:4, 3:2, or Auto ratio. You really just need to experiment to see what allows you the highest OC on your processor.

But I know you are probably wondering, why not just unlink? Well, the ratios are there for a reason. Those ratios allow the computer to be more in-sync. For this reason, sync mode is the best, but as I've stated, it wouldn't make sense in your situation.

Also, remember to turn off the spread spectrums and the power-saving features! You can re-enable the power-saving features later once you are stable.

Also, remember the infamous EVGA 680i vcore droop. If you set the vcore (aka the CPU Voltage) to, say, 1.30V, it will actually put out 1.26-1.28V. It's important to keep this in mind, so you don't starve your processor of the necessary voltage.

Edit: One last thing. Make sure to flash your BIOS to the P31 BIOS. Before I did it, my processor couldn't go an inch above 3.2ghz. Now I've gotten it up to 4ghz. Essentially, the P31 BIOS helps out overclockers, so you probably want it.

Edited by stettybet0, 25 October 2007 - 01:55 PM.

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#3
stearmandriver

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Hey, thanks for the response. Thanks especially for the heads up about voltage droop... didn't realize that.

Can you clarify one thing? You say that, in my case, it wouldn't make sense to leave them linked because I'd only get about a 400Mhz FSB bump before I hit the RAM limit. Can you tell me how you're figuring that? This is where I must be missing something.

It seems to me linked and synched makes MORE sense for me than you because I'm starting with a lower FSB (800 Mhz) than you. If we're both using DDR2 800, and RAM speed is double-pumped while FSB is quad pumped on an Intel board, our FSB limit is 1600 Mhz before we hit our RAM limit of 800 Mhz (assuming a 1:1 ratio), right? That means you (starting with a faster chip at 1333 Mhz) can only bump your FSB 267 Mhz before hitting 1600 Mhz, while I can bump mine 800 Mhz.

Given that I'm using a slower chip with a higher multiplier, 1600 Mhz FSB gives a clock speed of 4.4 Ghz. Obviously I'll never achieve that, so shouldn't I be ok linked and synched since I'll never hit the RAM limit then?

Apparently I'm misunderstanding something. If you or anyone else could point it out thatd be great!
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#4
stettybet0

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I'm sorry if I wasn't clear. I do recommend leaving them linked, just not syched.

Here's why I don't recommend syched: As we both agree, it's very unlikely that you will be able to get your FSB to 1600mhz. And unless you do that, your RAM will be running below it's rated speed. You don't want that. In this case, your CPU would be holding back your RAM. Both are important in system speed.

As I also mentioned, I don't recommend a 1:1 ratio either: With a 800mhz FSB, your RAM would be running at 800mhz too. Sounds nice, but once you start overclocking, it might not be. In my experience, the FSB will overclock more readily than the RAM. So, in this case, your RAM would be holding back your CPU.

This is why I recommended that you experiment with the 5:4, 3:2, and Auto settings. You probably want to run your RAM at no more than 900mhz if you want to keep tight timings (which are just as, if not more, important than raw speed). Also, you want this because if you go any higher, you might need more than 2.2V, and the 680i has a history of problems with RAM voltage above 2.2V...

So, with your RAM at 900mhz:

a 5:4 ratio would give you a 1125 FSB and a 3094mhz CPU. Not bad. You should be able to do that no sweat.
a 3:2 ratio would give you a 1350 FSB and a 3713mhz CPU. This might be a little harder. You will need very good cooling to do this, and well as high (at least compared to what Intel recommends, which is no more than 1.35V) voltages. Or, your chip might just be a runt and not be able to do this speed.
I'm not sure what an Auto ratio would give you, as I think it's different for every chip.

So, unless you have very good cooling and are willing to risk the high voltages, a 5:4 ratio should be good for you. But you might want to check Auto and see what it gives you. I wouldn't try much past 3.2ghz to start, though.

Edit: Also, when you start to OC, don't leave the CPU voltage or RAM voltage on auto. It will over-estimate and might damage your parts, or at least cause them unneeded stress. My e6750 runs at 3.2ghz with 1.31V set in BIOS (about 1.28V after droop). If I leave it on auto, it sets the voltage to 1.41V! It runs at 3.6ghz with 1.45V set in BIOS (about 1.41V after droop). I haven't put it on auto at this speed, because it would probably put the voltage up around 1.55V, which would burn up my chip. Use those voltages as guides for what you need. Then stress test, make sure you're stable, and then lower voltages until you get as low as you can go while being stable.

Edited by stettybet0, 25 October 2007 - 07:12 PM.

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#5
stearmandriver

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Dude... PERFECT. Now I understand. Sorry to make you explain some of that twice, but thanks a LOT.

After I do this I'll make another post of my results in this thread, in case it'll help anyone else in a similar situation.
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