Use DDR2 800 on DDR2 553/667 Motherboard

Hi Experts

A question came up last evening between a couple of friends and I and as none of us knew the answer, I thought I would ask someone who would.

If you have a motherboard that says to use DDR2 533/667 memory sticks can you use a DDR2 800 memory sticks instead?

Could you explain why just for completeness please?


Martin CotterillDabblerAsked:
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Mark DamenERP System ManagerCommented:
The answer is probably YES.  It is possible to use faster RAM than that is required, as most memory is quite happy clocking itself down to run at the correct clockspeed for the motherboard.  What is not a good idea, is mixing 800Mhz with 667Mhz because it causes an inbalance.  I have successfully used 667Mhz RAM in a board which specified 533Mhz.

So the answer is yes you can, just dont mix RAM modules of different speeds.

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You can usually use faster memory in your PC, providing it is the same type, however, you won't necessarily get a performance increase as the throughput is usually constrained by the speed of the Front Side Bus (FSB).

A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum throughput of 10,664 MB/sec. (on paper at least), which is a good match for 667 MHz DDR2-SDRAM (= 333 MHz double-pumped)  that has a maximum throughput of 10,672 MB/sec in dual channel.

However, you could overclock the processor in which case the faster memory may help as it will allow more throughput.

RAM is rated for the fastest speed it can operate at and remain stable, so running it at a slower speed is not a problem.  The only exception were the bad old days of SDRAM when certain motherboards could only work with certain brands, and when PC100 and PC133 were made with low density chips and motherboards were designed to only use those types.  In that case, even the same speed RAM would not work, unless the modules were made with the correct RAM density.
Martin CotterillDabblerAuthor Commented:
Thanks both

That answers the question brilliantly.

I'll split the points equally between you if I may as both answered the question from different viewpoints. markusdamenous from experience and Milleniumaire from a technical standpoint.


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