DDR Speed Question

Some questions regarding DDR (rated) speeds.

If the motherboard supports/recommends DDR-400 (PC3200) and you use DDR-333 (PC2700), what are the usual results -- assuming you are using fairly good quality RAM, such as Cosair/Crucial/OCZ, etc.? Will it even POST successfully, or does this depend on the motherboard (manufacturer, quality, etc.)? Will it just slow down the whole system to DDR-333 speeds? Will it even be stable? Can you somehow force the system to run DDR-333 at DDR-400 speeds (not sure if this counts as overclocking the RAM)?

Can anyone provide any good external links that address DDR RAM speeds?

Thanks,

Tell us about the other components. MB, CPU etc.

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Originally Posted by gkline

Tell us about the other components. MB, CPU etc.

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Sorry, it was meant as more of a general theory type question. I don't have any specific brands/components in mind. Just curious if (on average, more or less) slower speed rated RAM can still be used in newer equipment -- and if anyone has successfully done so.

With the old PC-100/PC-133 type of RAM, the CPU multiplier and FSB was fairly dependent on the 100/133 nature of the RAM. If you had a 933 MHz CPU for example, you could still use PC-100 RAM, but the system would slow down everything else to much less than 933 (sometimes down around 500 MHz). However, if you had an 800 or 1.0 GHz CPU, you could run PC-100 or PC-133. Didn't matter -- just the PC-133 would only be running at PC-100 speed. So what I am wondering is, "How dependant are new/current motherboards on the RAM speed?" I would imagine there is still a FSB/system speed calculation system, where everything probably runs at the least common divider, but how does the current world of overclocking fit into this?

Hypothetically speaking, for example, would DDR-333 RAM work in a new AMD 64 based system -- but just slow everything down because it is only 333 rated, instead of 400 (or higher)? I have heard that higher speed rated ram, such as 433 (when you only need 400) is good if you want to overclock your system. Does this work in reverse?

As long as your mobo's Bios supports memory dividers to allow slower speeds than stock HTT (400), yes, you can use slower memory.

I just gave my kids my old setup. A-Bit nf7-s v2,amd xp 3200+.
Both are meant to run @ 400mhz,yet I can run it with one stick of 333.
All I had to do was change,the ratio of cpu to ram and it ended up running at 400 mhz.Incidentally,it runs better now,than it ever ran for me. LOL