DDR 333 VS DDR 400

[minnesotanewbee]

First, let me say I am new to this forum and my knowledge of hardware is average. There is one thing I am unsure of, however. Is it possible to run DDR 333 on a motherboard rated for DDR 400? and, can you run both DDR 333 and DDR 400 on the said motherboard (a 1 gb stcik of each)? I realize this is somewhat of a basic question, but it will tell me if I upgrade or not....

Thanks for any info in advance

 

[Heidfirst]

RAM is usually backward compatible within the same form factor so yes although there may obviously be a small drop in performance.

As for your 2nd question it may be but you would have to run both DIMMs at the speed of the slower.
Running mismatched DIMMs is a bit of a crap shoot though, sometimes it works & sometimes it doesn't.

 

[minnesotanewbee]

Originally posted by: Heidfirst
RAM is usually backward compatible within the same form factor so yes although there may obviously be a small drop in performance.

As for your 2nd question it may be but you would have to run both DIMMs at the speed of the slower.
Running mismatched DIMMs is a bit of a crap shoot though, sometimes it works & sometimes it doesn't.

cool, thanks for the info.

 

[Peter]

Note that some chipset architectures force you to use a certain (minimum) RAM speed to match the bus speed of your CPU. While what's been said is generally true, sometimes it isn't as easy. Check your stuff. What board, what processor is your question about?

 

[minnesotanewbee]

Asus

going from a P4S8X P4 2.4 gb to a /asus A8N-SLI W/A AMD 2.4 ATHLON X2

 

[Peter]

Ok ... the SiS chipset on your old board is fairly flexible in FSB/RAM speed ratios - and on the Athlon64 architecture, where the RAM is attached directly to the CPU, there are no such ratios at all, and thus no limitations. You'll be able to run DDR333 RAM just as well as DDR400 or even DDR200 if you please.
Mind that the latest platform (AM2) uses DDR2 RAM. You'll have to go with the older socket-939 platform for DDR.

 

[minnesotanewbee]

Originally posted by: Peter
Ok ... the SiS chipset on your old board is fairly flexible in FSB/RAM speed ratios - and on the Athlon64 architecture, where the RAM is attached directly to the CPU, there are no such ratios at all, and thus no limitations. You'll be able to run DDR333 RAM just as well as DDR400 or even DDR200 if you please.
Mind that the latest platform (AM2) uses DDR2 RAM. You'll have to go with the older socket-939 platform for DDR.

the asus A8N uses DDR (PC 3200), so I think I'm ok. Thanks alot for the info....

 

[kmmatney]

You shouldn't have too many problems. The BIOS will automatically set a memory divider to run your memory near its rated speed. Actually it will probably run even a tad lower than DDR 333, since the memory dividers usually round down.

 

[Peter]

You can do the math yourself - divide CPU speed by your RAM's true clock speed (166.67 MHz for DDR333), round down, that's your "memory divider". Ex. if your CPU is running at 2200 MHz (non-overclocked), you'll get 2200/14 = 157 MHz or "DDR314" if you so please. Overclocking will push the CPU and RAM speeds alike.