DDR2 Dual channel config query :-)


I'm currently running 2x1GB 667mhz DDR2 ram on a Asrock 775Dual-VSTA mobo.

I will be replacing this mobo with a Asrock P45XE as my ATi 4870 is only able to run at Pci-e x4 and I also want more than 2gb Ram which is this boards Max capacity. (I'm running 64 bit Vista and the Windows 7 64bit beta)

My query was partially answered by this boards FAQ but I was hoping someone could clarify for me.

Basically the new mobo will have 4 DDR2 slots. I will be ordering a 4GB Kit (2x2GB) with it but would like to use my 2GB Kit (2x1GB) as well. The new 4GB kit will be 800mhz where as my 2GB kit is 667mhz. If I run the 4GB kit in slots 1 & 3 and the 2gb kit in slots 2 & 4 will the 800mhz ram be clocked down to 667mhz?

If so will I notice much of a performance hit compared to 2 kits running at 800mhz?

Cheers, Phil.
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  1. It will clock down to 667Mhz and you'll lose 2-3% performance. If that bothers you, you could sell the 2GB kit and get two 4GB kits for a total of 8GB. Only you knows if you really need more than 4GB.
  2. Thanks for the reply.

    I'll porbably try it with the 4+2 gig first if the performance loss isn't all that high. Then I'll see wether my future needs will require any more ram.

    Thanks again, Phil.
  3. If your CPU has an FSB of 333 MHz then it'll actually perform slightly better at 667 than at 800. Odd, no?
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