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I am planning to buy this memory. I don't understand what 9-9-9-24-2N means vs a timing like 9-9-9-20? Does it matter in performance?

A related question: what's the difference between buying the above 16GB vs buying two of these? The second option is cheaper.. Is this worth it?

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2 Answers

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Those numbers describe different latencies that are incurred during memory access. The larger the numbers, the slower the memory.

Here are the gory details: http://www.techpowerup.com/printarticle.php?id=131

Besides brand, the primary difference between your two choices is 1.5V versus 1.65V. This can be a real issue if your motherboard doesn't support one or the other.

Always check the motherboard manufacturer's memory support list. If your motherboard is new, you should be able to find memory that is guaranteed to work on your system. Older motherboards can be hard to find matches for given the short half-life of memory products.

At the very least, see if the preponderance of large DDR3 on the supported list is 1.5V or 1.65V.

In addition, since you are installing a very large amount of memory, verify that your Power Supply is of high quality and sufficient amperage on the system board side rails. Most power supplies become a bit unstable (large ripple and voltage variances) when taxed at their maximum on one rail. If you have two CPU's as well, your system may not be well supported by a gaming power supply that expects the big loads to be on the peripheral rails (dual video cards, RAID, etc.).

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The page says a lower number means faster but is it important enough that it makes a real different? Numbers by themselves don't mean much or I can't relate. – Tony_Henrich Jun 25 '10 at 17:54
The MB supports both 1.5v & 1.65V and more. My PSU can handle the load. The MB manual lists only one 4GB stick which is Kingston and that's a lot more expensive than the two I mentioned. – Tony_Henrich Jun 25 '10 at 17:57
One more thing: The page doesn't explain the last number, 2N. – Tony_Henrich Jun 25 '10 at 17:59
2N is the command rate, or command timing. 1T or 1N is faster but 2N/2T is often more stable. I can't find a good explanation; chances are you'd have to refer directly to the JEDEC docs. – kmarsh Jun 29 '10 at 12:31
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The numbers refer to clock cycles, so if you're comparing PC 1333 with PC 1600, larger numbers on the PC 1600 would actually indicate similar performance. so 7-7-7-20 on PC 1333 should perform similarly to 9-9-9-24 on PC 1600.

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