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I have 3 DDR3 sticks of GEIL memory that says 1600 on the box. First it was reported as running at 1333 by my OS so I changed those values from 1333 in my bios to 1600. However it still gets reported as 1333 (Anyone an idea why? Mobo: Asrock Supercomputer).

I don't really mind that really since I highly doubt the performance difference between 1333 and 1600 is really noticeable (correct me if I'm wrong).

Now I need to buy additional memory. I was wondering if memory of the same brand with the same RAS/CAS latencies but running at 1333 will be compatible with 1600 I have if I let them run at the standard 1333?

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I assume you are talking about one of the three Geil 1600 models listed here? that's just to confirm, since those are the three 1600 Geil sticks recommended. It's unlikely that you purchased 1600 but were shipped 1333... but still possible. – Bon Gart Jun 12 '12 at 19:32
The 1333 should be compatible with the 1600, if you decide to buy more. – user3463 Jun 12 '12 at 20:05
I have the box it's definitely 1600, also gets reported as such in the metadata. But it runs at 1333. – Lucas Kauffman Jun 12 '12 at 21:56

On some motherboards you have to enable XMP to go beyond the JEDEC standard 1333 speed. If you're using windows then you can use siv ( to show the full details of the dimms in your machine and their current timings (as well as almost anything else you could ever want to know about your machine). That said, if your bios has let you change the speed it might have done this already.

As for performance difference, when enabling the overclocking mode on my motherboard a 4 minute render time dropped to just over 3 minutes. Of course, this is also probably due to the processor being overclocked a little at this point, but the speed gained was more then the difference in processor clock before and after.

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