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DDR2 ratio with Core 2

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October 2, 2006 6:02:16 PM

I will get a Core 2 E6600 and Asus P5B Deluxe. I never got the relation between the CPU and the memory

Its been reported that with Asus last BIOS, you can change the moemory multiplier. What should I do with Core 2?

If I overclock to a 400 MHZ FSB, should I get DD2 800? Thats how I used to calculate P4. Or should I get 1:1 timings and keep DDR2 667 MHZ?

By the way, can anyone tell me if I have one memory configuration in dual channel and another slower memory configuration in other dual channe, will the lower config slow the faster one? (Got 2x 667 modules. might upgrade to 2x 800. Should I trow away the 667 modules or add all four together?

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October 3, 2006 11:02:55 AM

Hello! I think that you should go with 1:1 timing adn runing on 667MHz.
And you must use the same type of memory modules for dual chanel with same operating freqfency I mean you must use onlu 667 or only 800 MHz modyles if you want your PC to keep runing with no misakes and no crashes!
October 3, 2006 11:43:16 AM

Don't waste your money buying rams just to have a 1:1 ratio. With the 667 you should be able to overclock that cpu, even with the uneven ratio still you have a faster performance. I have tried this by borrowing my buddies 667 ram to replace my 533 for the 840, both setup overclocked but I have no significant improvements in performance in gaming other than I have 1:1 ratio. But if you can afford to get DDR2800 then do so, you might be able to sell them old ram for the upgrade. Either way, you won't get any big performance increase. Just read the article in Corsair Dominator rams and benchmarks, them high speed rams don't get much performance over DDR2800 which don't have big performance over DDR2667. The good thing about higher frequency rams, is they offer more headroom for overclocking. But first try overclocking your E6600 with that DDR2 667 if you can manage to overclock it to whatever you desire then it's good for you. If not then go ahead and get them DDR2 800.
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October 3, 2006 12:11:05 PM

And if you dont OC or do a small OC then you can usually lower the timings on the faster ram at the least.
October 3, 2006 12:38:21 PM

I would say get the DDR2-800, since that is pretty much the standard for enthusiasts everywhere. Yes, it doesn't offer that much of a performance gain, but it doesn't cost too much more than 667 ram either.
October 3, 2006 12:48:49 PM

Hi,
You definetly want to stay 1:1 with a C2D. The guy who said his PentiumD840 ran well with asynchronous memory is correct; the longer instruction queue of the Netburst will allow that to operate well. The C2D has a shorter "pipeline" and therefore suffers with asynchronous memory. Also, C2D needs tight timings, not high memory frequencies, to run well. I would suggest you get low latency DDRII667, or if you can afford it, low latency DDRII800. The stock FSB is 533, so DDRII667 will give you a lot of headroom for OC'ing with air cooling. If you're going to REALLY OC it, then you'll need the 800 but remember, get LOW LATENCY, CAS 4 or 3, preferably 3.
October 3, 2006 3:13:05 PM

I will get new Ram because my current modules suck, they are 667 DDR2 but with very high latency. I will get corsar low latency. I am willing to spend as much as necessary to get the best ram.

Stock settings for E660 are 2.4GHZ (266 FSB x 9) The Asus P5B Deluxe lets you lower the E660 clock multiplier, Anandetch reported achieving 3.62GHZ (400 FSB x 9, thats stock multiplier) and 3.56GHz (445 FSB x 8, lower multiplier)

Lets say I go with 400 FSB, shoulnt I go with 800 MHZ DDR2? Or will even 533DDR2 be fine? As far my knowlegde goes, 800 MHZ DDR2 is actually 400 MHZ and 667 MHZ would only be ok if the CPU FSB didnt go higher then 333MHZ...

...again, because I tought ratio was 1:2 (CPU x memory) What the hell is 1:1?
October 3, 2006 8:54:55 PM

Good questions all; I will try to answer them as best as I can. 1:1 means that for every clock cycle that the CPU requests data, the memory is there to give it. This is called SYNCHRONOUS clock settings. Any other setting is ASYNCHRONOUS, meaning not in sync. The CPU may have to wait for data from the memory, even if the memory is running at a higher frequency. A CPU with a deep pipeline (Like the P4 and PentiumD)will not suffer from this, because it can do other things while waiting for the memory. A CPU with a short pipeline (Like the P3 and all Athlon XP's and Athlon 64s) will suffer, because if it has to wait for memory it wastes CPU cycles. I know that FSB266 is equivalent to DDRII 533, FSB333 matches DDRII667, and FSB400 goes with DDRII800, but I do not know how the clear discrepancies are worked out. Perhaps since the memory is exactly double the speed of the FSB the memory is always ready when the CPU wants data.

One side note: memory is NOT the most important factor in the speed of your C2D system. If you're a gamer, $50 saved on memory and put into a GPU would be well worth it. As a general user, $50 saved on memory and spent on a water cooling unit for higher OC's would be good also(you would also need a CPU with a higher multiplier for that scenario)

Hope this helps!
October 3, 2006 9:53:25 PM

Judging by what I read, I may say the following: (By the way, thanks a lot!!!!!)

1) Conroe E6600 has short pipelines and need low latency plus synchronous memory wich is 1:1. That means pairing a 400FSB with a 800DDR2 (Because its actually 400)

I think I will overclock it to 400FSB, thats easy. Higher overclock with lower multipliers would mean getting 5-5-5-15 latencys by kingston. The only 4-4-4-12 modules I get are from corsair and for 800DDR2 or the ULTRA EXPENSIVE 1111DDR2 wich Im not willing to afford right now (will move in 2 years and buy new PC)

I alredy have a Watercooler and a 7950gx2 (the reason why Im getting new mobo, cpu and ram)

I still have one doubt. Is it possible for even synchronous system for the cpu to have to wait for the memory and therefore would be a good idea to build a Asynchronous system with a higher memory speed?
October 3, 2006 11:58:05 PM

Here's a link to the article I got my info from. http://www.madshrimps.be/?action=getarticle&articID=472 As you can see, it is possible to achieve faster speeds with asynchronous memory, but it get very expensive. You seem like price is no object(or almost no object) so you may want to go with asynchronous. On the other hand, you can see in the SuperPi and 3dMark scores, DDRII667 with 3-3-3-8 timings is BARELY faster than 533, but 800 pulls away pretty well, especially with 4-4-4-12. What you have to realize is that in the article, they didn't OC, so their scores for everything BUT 533 was asynchronous. If you bought the DDRII800 and kept it synchronous, with the FSB somewhere North of 300, I think that will be the best total performance.
October 6, 2006 2:20:04 PM

To make a long story short, according to the article posted above, if you're going to be overclocking your C2 Duo than get DDR2 800 speed ram, otherwise get fast DDR2 533 speed ram. It runs better and is cheaper than 667 speed rams.
October 7, 2006 11:57:54 PM

I tried 1:1, but I'm getting my best results with 4:5 (Memory Multiplier 2.5), with the FSB at 344. This gives me DDR2-860

With 5-5-5-12 timings I get
PCMark 8127
!