OC Q6600: Is my memrory to fast or too slow??

[oldman55]

I am somewhat new to over clocking and have this question.

I have just finished building a system with Intel Q6600 with Corsair 800 speed memory.

Do I speed the FSB/CPU clock up to match my memory or
speed the memory clock up to match my FSB?? let me explain.

The front bus on the Q6600 runs a real clock rate of 266mhz (266 X 4 quad pump) for and effective rate of 1066mhz. So the FSB has a bandwidth of 8533MB/s (1066 X 8 )

My Corsair memory is running at a clock rate 400mhz X 2 clock edges X 8 = 6400MB/s

So it would seem that I would have to over clock my memory to keep up with the FBS
but I have read you want to keep a ratio of 1:1 for FSB to memory clock so do I raise the
FSB to 400mhz ???

 

[pavel-]

raise the FSB of your CPU to match the 400mhz RAM.

 

[oldman55]

it seems that if I raise the FSB clock up to match my memory it will
increase the gap in bandwidth between the FSB and the memory??

 

[krazynutz]

1. What kind of motherboard do you have? Research on how you set the RAM to run @ 1:1 with your CPU before OCing.

2. Is your RAM Cas 4 or Cas 5 Corsair PC6400?

Rule of thumb: Lower the speed of your RAM to match your FSB. For example, at stock speeds, your motherboard will run your CPU @ 266Mhz (533Mhz) and your RAM @ 400Mhz (800Mhz). What you want to do is lower your RAM to 266Mhz (533Mhz) so it runs in a 1:1 ratio with your CPU. THEN you can start overclocking it. As you raise the FSB, both the CPU and the RAM will raise simultaneously. Below is a very crude chart @ 1:1 ratio:

FSB 266Mhz = CPU @ 2.4Ghz, RAM @ 533Mhz
FSB 333Mhz = CPU @ 3.0Ghz, RAM @ 667Mhz
FSB 400Mhz = CPU @ 3.6Ghz, RAM @ 800Mhz (stock speed for RAM)

If you have Cas 5 PC6400 RAM and a stable OC @ 333 Mhz, you can probably lower the timings of the RAM to 4-4-4-12. If you have Cas4 PC6400 RAM, you might be able to get by on even tighter timings @ 333Mhz. Remember, start low with the FSB and go up. You'll probably not get to 400Mhz with the Q6600. When you get to a nice, acceptable OC, try tightening your RAM timings to make up for the lower FSB speed. Whatever you do, DON'T change the first timing to 3. You won't even boot.

For more info, read graysky's OC post for Core 2 Duos and Quads. I think it's under the CPU section of OCing.

Good luck!

 

[oldman55]

Krazy, thanks for the info and the help. So it more about clock rates
then actual bandwidth of the of the FSB and the memory bus?

 

[krazynutz]

Basically, if you want your system to be stable, you have to lower your RAM speed or else it'll go up waaaaay higher than specified, thus, crashing your system before it boots or shortly thereafter.

If you don't want to OC, then set your RAM at it's stated speed and leave the FSB alone. That way, you'll have the following scenerio:

FSB = 266Mhz, CPU = 2.4Ghz, RAM = 800Mhz

If you OC with these settings, say to 333Mhz FSB, then your RAM will go significantly higher than 800Mhz (don't know exact rate) and you probably won't even boot.

So, to OC properly, it's best to match your RAM to your FSB and go from there. Everything will raise simultaneously. You can't set your RAM at 800Mhz and OC your FSB/CPU independently. They all move together. If you don't get up to 400Mhz FSB (which will give you 800Mhz on the RAM) then tighten the timings on the RAM. This will increase bandwidth as well. Hope that helps.

 

[hminh87]

Why does the RAM speed need to be lowered before OC?
I though the RAM will automatically running @ 800MHz if the FSB is set to 400MHz and the ration will be 1:1 just like that.

Yes, I'm a OC noob.

 

[krazynutz]

Yes, the RAM WILL be running @ 800Mhz if the FSB is running @ 400Mhz. But for that to happen, you have to lower the RAM to 533Mhz first to keep it in a 1:1 ratio with the CPU. That way, when you raise the FSB to 400Mhz, it'll bring the RAM back up to 800Mhz.

For example, if you have PC6400, and run at stock speeds, your motherboard will run it in a 2:3 ratio:

FSB: 266Mhz = CPU: 2.4Ghz = RAM: 800Mhz

If you OC to 400Mhz successfully, then you'll have a 1:1 ratio with your RAM running at stock speeds.

FSB: 400Mhz = CPU: 3.6Ghz = RAM: 800Mhz

You can't just jump right in and put your FSB @ 400Mhz. You have to work your way up.

 

[hminh87]

Magick, mate.
I will keep this in mind once my system arrived.

 

[krazynutz]

cool. Let us know how it goes! Good Luck!

 

[skyguy]

With the Q6600's, you got more or less 2 options:

1) lower the CPU multiplier, set your FSB:RAM to 1:1 and jack it up.....get the RAM back to around 800 and hope your cooling the CPU is good enough to get the FSB high to match

2) keep the 9x multi, crank up the FSB and change the RAM multi to 4:5 and hope it stays stable (assuming your RAM is overclockable and good stuff). If not and it can't go to DDR-900 or beyond, then go to Option 1, or else run your RAM below the speed speed (ie--DDR2-720 or something, however high you get your FSB).

 

[krazynutz]

I tried lowering my multiplier on my Q6600 to x8 (on an ASUS P5B-Deluxe) and it did some really wacky stuff.

My system runs beautifully @ 9x333 @ 1.275v. I wish I could say the same at 8x375. Even if I up the FSB voltage to 1.3v (which I did for my e6400 @ 400Mhz - 3.2Ghz), it didn't help. Was horribly unstable and even wackier, the bios, POST screen, and windows NEVER gave me the real speed of it when I changed the multiplier.

At 266Mhz FSB, these are the "speeds" of my CPU in POST/BIOS

x6 - 12.42Ghz WTF?
x7 - 3.11Ghz WTF?
x8 - 2.66Ghz WTF?
x9 - 2.4Ghz (normal)

Why would changing the multiplier do such crazy things? Also, I've had my e6400 @ 3.2Ghz @ 1.325v. If my Q6600 works just fine @ 9x333 (3Ghz) with 1.275v, why wouldn't it work just as well @ 8x375 @ 1.275v? Why would it need any more voltage to run at the same speed? My RAM is PC6400 and I had it @ 2.1v so I know it's not the RAM.

Why such instability at the essentially the same speed? I'm making a new post for this!

 

[skyguy]

No, it's more about the FSB than the overall speed. The higher the FSB, on average, the higher the vCore you need. 1.325v is nothing......truly. To start hitting high clocks you'll likely need volts approaching 1.40v. I know that sounds scary, but it's still WELL within the tolerances, not a problem.......except cooling. I have a watercooling setup, so I can push the FSB to 450x7 if I want or go 380x9.

So as you raise FSB, even though the speed might be the same overall, you need to raise vCore as well. Dunno how much exactly, too many variables to guess here on a forum, but suffice it to say you'll need to start cranking up the volts.

So the question ultimately is: where is the cutoff? When you need to start increasing voltages alot and you're only getting a couple hundred mhz speed increase in return, my opinion is that's not worth the tradeoff anymore. Unless you have some very good cooling, it's better to back off the FSB and find a very nice happy medium for temps and speed. Sure, I can claim high clocks, but it comes with a price........thankfully I have the cooling, but not everyone does.

So keep that in mind. There is ALWAYS a point at which it's no longer worth the risk.....that point is different for everyone. So find your happy place and then just enjoy the scenery

 

[krazynutz]

Yeah, I can do 3.2Ghz (8x400) @ 1.325v but the extra heat (hitting high 60's during load sometimes) doesn't really justify the relatively negligible gains. I have an old Thermalright XP120. It does the job well enough and to replace it ($45-ish purchase) doesn't really justify the higher speeds either. I don't care about bragging rights. Just 3D (studio max) rendering times. Thanks for the input!

But the question remains - why do I get such wacky "speeds" when I change my multiplier?

 

[Hatman]

Personally I wouldn't go over 1.35vcore unless I had water cooling, I have what I consider high end air and I don't think its enough to get over that safely.