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[Memory] DDR2: Which is fastest?

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February 2, 2009 5:59:07 PM

Can a memory expert explain this to me?

In a recent Tom's Hardware memory article, 4GB Gets Cheap: 9 Dual-Channel Kits, Thomas Soderstrom reviews 9 memory kits at voltages 1.8V, 2.0V, and 2.2V. He attempts to run each of the 9 pairs at 800MHz, 1066MHz, and 1200MHz.

I purchased the Patriot Viper 6400LLK memory featured in that review. My question is, "Which is fastest?" And secondary, "Can I use any of those with my Intel Core 2 Duo E7400 processor on a Gigabyte GA-EP45-UD3P board? Or do my CPU settings affect what data rate I choose?

Here are the timings at 2.2V for Patriot Viper 6400LLK:
DDR2-1200 @ 7-7-7-11
DDR2-1066 @ 5-5-5-6
DDR2-800 @ 4-4-4-4

Here's another hypothetical: Assuming equal timings, how much faster is memory at 1066MHz than 800MHz?

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a b } Memory
February 2, 2009 6:23:07 PM


Quote:
Assuming equal timings, how much faster is memory at 1066MHz than 800MHz


PC2 6400 or any RAM running at 800 MHz. has a data transfer rate (speed) of 6.4 GB/second data transfer rate.

PC2 8500 @ 1066MHz = 8.5 GB/second data transfer rate 'speed'.

February 2, 2009 7:15:58 PM

I tried reading the stickied post in the Memory forums, but it was hard to follow. So this may be a dumb question. Are memory speeds and CPU speeds related? For example, if I run my Intel Core 2 Duo E7400 @ stock, would tight timings on 800MHz be better? Or would more relaxed timings on 1066MHz be better?
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February 2, 2009 9:46:01 PM

Are my conclusions correct? My best setting is DDR2-1066 @ 5-5-5-6 timings. Although bandwidth increases at DDR2-1200, latency also increases. My lowest latency is at DDR2-1066. DDR-800 @ 4-4-4-4 offers no benefit.

If I understand correctly from the article, then, for my memory at each test Timing below:

DDR2-800 @ 4-4-4-4 Timings
Latency equals 10ns
Bandwidth is 6.4Gb/s
Reason: Straight from table for ns latency

DDR2-1066 @ 5-5-5-6 Timings
Latency is slightly less than 10ns
Bandwidth is 8.5Gb/s
Reason: DDR2-1000 @ CL5 is rated at 10ns. However, looking at the tables you provided, if memory with CL=4 held on from DDR-800 to DDR-1000, latency (ns) is reduced from 10ns to 8s. Therefore, if CL5 @ 1066 has less latency than CL5 @ 1000.

DDR2-1200 @ 7-7-7-11 Timings
Latency is between 10.49ns and 12.17ns
Bandwidth is 9.6Gb/s
Reason: DDR2-1150 @ CL7 is 12.17ns, DDR2-1333 @ CL7 is 10.49ns. Since DDR2-1200 is in between, latency is in between.
a b } Memory
February 2, 2009 10:47:33 PM

The Patriot PC26400 posted is guaranteed to run at 800Mhz. @ 4-4-4-12 with 2.2v. Well, I would set it there in BIOS and check for stability. There is no guarantee the RAM will run at 1066MHz. by the Mfg. But, if you loosen the timings to say 5-5-5-12 it should get close to those speeds, but no guarantee. If you were overclocking the system BUS to attain faster CPU transfer rates that procedure takes the RAM with it to faster speeds. The RAM is a component dependent on the system BUS speed as is the processor. RAM has dividers built in to the BIOS and is adjustable to perform speedwise within the BUS system in that manner. Having the RAM set to a higher rate via a BIOS divider may not always produce the best performance result regarding RAM performance. MB chipset and BIOS capability make a difference. It would only make sense to loosen the timings to reach needed faster data transfer speeds. Like when OCing. A lot of RAM Mfg.'s have PC26400 DIMMs that are rated at 4-4-4-12 @ 1.8-2.0v. Run as fast with less power needed. These are all just a few variables to think about.
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