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I currently have a 2x2GB RAM kit with the following specs (link):

  • DDR3
  • 1600MHz
  • 7-8-7-20 latency

I want to buy another set, but I couldn't find the exact model anymore.

So, I'm thinking of getting this kit, also by Corsair. The only difference is the latency: 9-9-9-24.

What would happen from the difference in latencies?

And what if I chose this 2x4GB kit? Would performance suffer even more?


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Well, I would not reccomend it. Some motherboards will detect the mismatch and automatically compensate by running at the lesser of the two - but this might not always work. Generally, it will cause instability in your system. With the low cost of dynamic memory these days, why not just buy a 4x2GB, matched kit?

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Is there a way to make sure my motherboard will support it, before I make the purchase? – Dor Nov 9 '12 at 10:03

The memory will adjust itself to the slower set, but the main thing you need to look at is the voltage.

Memory running at different voltage can cause issues, including BSOD and refusing to boot. (source)

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As I wrote, the only difference is the latency. Voltages are the same. So would that pose a problem? – Dor Nov 8 '12 at 19:36
if voltages are the same, then there should be no issues, apart from the adjustment the motherboard will make that will run all memory at the same (slowest) speed. unless you are into extreme overclocking, you are not likely to notice any difference – SeanC Nov 8 '12 at 19:49

The motherboard will run the memory at the lesser of the two speeds. You would loose a tuiny bit of performance.

However adding more memory (and potential disk buffers) is likely to speed up your system with a larger factor. I recommend adding it. It should improve performance for almost everybody.

(The people not showing a performance increase would need to do something which does not require more than 4GB memory yet does involve heavy cache misses/memory access. I might be able to construct such a thing - with effort. Doing that in day to day usage should be extremely rare).

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