PDA

View Full Version : Need help understanding RAM speed


Kain
10-09-07, 05:48 AM
I'm planning on building a computer with the Q6600 and since it has a 1066MHz FSB do I need 1066MHz RAM? I read around and it seems you can overclock higher with faster RAM?

CaptNKILL
10-09-07, 06:08 AM
I'm planning on building a computer with the Q6600 and since it has a 1066MHz FSB do I need 1066MHz RAM? I read around and it seems you can overclock higher with faster RAM?
The main thing to remember when talking about a Core 2's bus speed and RAM is that the FSB is 2x the "real" bus speed.

To run a 1066Mhz FSB CPU at 1:1 with the memory, you'd only need DDR2-533 ram. If you use faster ram, it'll run at something other than 1:1 by default. If you bought 1066Mhz ram, it'd run at 1:2.

Once you overclock, you'll have to mess with the settings manually.

If you're getting a Q6600, DDR2-800 should be fine. If you managed to get it to 3.6Ghz stably, it'd be at 1:1.

If you really think you can push it further than that (which isn't likely unless you're getting a G0 core and water cooling), go for some DDR2-1066 for some extra head room.

Kain
10-09-07, 06:23 AM
Thanks. :)

What would happen if I overclock and the FSB exceeds the RAM speed?

CaptNKILL
10-09-07, 06:51 AM
Thanks. :)

What would happen if I overclock and the FSB exceededs the RAM speed?
Good question. :D

Basically, you'll be overclocking your RAM.

Back in the pre-DDR days this actually helped improve performance, but these days overclocking your RAM will do nothing good for you, and it can create some of the nastiest instability problems you'll see on a PC. Unstable memory can really screw up your PC pretty badly by corrupting things that are loaded into memory (which can then be saved to the hard drive in their corrupt state).

Most ram these days can take a small amount of overclocking, but I'm not really sure how much, and it depends on a lot of factors. I never overclock my memory unless I just need to squeeze a few more MHz out of something to round out my CPU speed to an even hundred. There really is no point to it at all other than to get a couple more points in a benchmark or to make your system specs look more leet. :p

In short - increasing FSB when your memory is already at its rated speed will overclock your memory, and overclocking your memory gives you no performance benefits and causes instability. The best way to avoid this is to get faster ram.

Kain
10-09-07, 07:07 AM
So, stock, the Q6600 runs at 4.5 x 533MHz = 2.4GHz or 2.25 x 1066MHz = 2.4GHz?

CaptNKILL
10-09-07, 07:19 AM
So, stock, the Q6600 runs at 4.5 x 533MHz = 2.4GHz or 2.25 x 1066MHz = 2.4GHz?
Well, the multiplier is 9x, so its actually 9x266.

I guess I should have said that the CPU FSB is 4x the "real" FSB and the memory (at 1:1) is 2x the "real" FSB. At 1:2. the memory is 4x the "real" FSB.

Its not as simple as it used to be, thats for sure. :p

Kain
10-09-07, 07:48 AM
So at 9 x 400MHz = 3.6GHz and DDR2 800MHz RAM will be at 1:1. Is that FSB possible? Is the P35 FSB overclock friendly?

Kain
10-09-07, 08:44 AM
One more question, what's the point in getting 1066MHz RAM when you'll never be able to hit that on the FSB for 1:1? Even at 4GHz, that's 9 x 445 MHz and 445 x 2 = 890 MHz RAM speed.

Madpistol
10-09-07, 10:10 AM
You're right Kain. There really isn't any point to getting 1066mhz ram if you can't go that high. However, that's not the case with a processor with an 8x multiplier, where the CPU will have to ride the FSB and ram speeds in order to get the highest possible overclock. 8x500=4Ghz. If you drop the multiplier down to 7x, now you really need some fast ram to get a good overclock. 7x500=3.5Ghz or in this case 7x533= 3.731Ghz. If you want to hit that high of an OC, fast ram really comes in handy.

If you have a processor with a 9 or 10x multiplier, you'll probably never use the full speed of the ram. The only way this isn't true is if you have a really nice watercooling setup or if you have an "exotic" cooling solution that cools below freezing temperatures (i.e. CO2, phase change, etc.)

Kain
10-09-07, 10:46 AM
Does the Q6600 have a locked multiplier?

Joe Public
10-09-07, 11:56 AM
Multipliers are locked upwards on all CPUs, except the "Extreme" models. You can lower the multiplier down to 6 on all Core 2 CPUs.

Kain
10-09-07, 12:09 PM
Thanks.

If I remember correctly, there is a way to see if a Q6600 is a G0 version from the serial number on the box. What am I suppose to look for?

cyntho
10-09-07, 12:35 PM
The end of the model # should say SLACR on it.

CaptNKILL
10-09-07, 04:38 PM
Can we sticky this thread? It basically answers all of the common questions we get from people wanting to upgrade to a core 2. :p

john19055
10-09-07, 06:25 PM
Just get some good DDR2 800 memory ,because running the memory at a higher speed then a 1:1 ratio gains you very little in performance .I ran my E6600 at 3.6gigs and use 800mhz so that it would be at a 1:1 ratio and then ran it at 3.6g at 1200mhz and I think I gained 50 to 100 points more with 3D06 .The 680i SLi IMO just has better stability when useing a 1:1 ratio.But sometimes when you do buy the faster memory like DDR2 1066 ,you are able to run it at lower lactecies at 800mhz .

Kain
10-11-07, 11:40 AM
Just get some good DDR2 800 memory ,because running the memory at a higher speed then a 1:1 ratio gains you very little in performance .I ran my E6600 at 3.6gigs and use 800mhz so that it would be at a 1:1 ratio and then ran it at 3.6g at 1200mhz and I think I gained 50 to 100 points more with 3D06 .The 680i SLi IMO just has better stability when useing a 1:1 ratio.But sometimes when you do buy the faster memory like DDR2 1066 ,you are able to run it at lower lactecies at 800mhz . So if I get a Q6600 and overclock it to 9 x 400 = 3.6GHz, that would mean 800MHz RAM speed. If I get 800MHz RAM I would have reached it's peak so would it be safer to get 1066MHz RAM in the same situation?

Secondly, you said that if you don't use the max speed of the RAM, you can run it at lower latencies. So will I get better performance with 1066MHz running at 800MHz than 800MHz RAM running at 800MHz? Will the system automatically detect this or will I have to set it myself?

Kain
10-11-07, 01:07 PM
BTW, is there any difference with 2 x 2GB vs. 4 x 1GB?

Kain
10-11-07, 08:16 PM
Say I have 800MHz DDR2 RAM that is rated at 3-4-4-15 and 1066MHz DDR2 RAM that is rated at 5-5-5-15. Does that mean if I were to run the 1066MHz RAM at 800MHz, could I beat the timings of the 800MHz RAM running at 800MHz?

Secondly, which would be better with 1066MHz RAM? Running the FSB/RAM (Q6600 clocked at 9 x 400) at 1:1 (1066MHz RAM running at 800MHz) with faster timings or running the FSB/RAM at 1:2 (1066MHz RAM running at 1066MHz) with slower timings (stock timings of 5-5-5-15)?

Libertysyclone
10-11-07, 09:52 PM
I personally havent seen a big enough difference to justify a large price difference for lower timings. in DDR they made a lot more of a difference.

Kain
12-17-09, 07:21 PM
What has been said in this thread, does it also apply to the Intel Core i7 processor? Is the "concept" still the same?