DDR400 vs DDR333

[SteveC]

Hi all,

I have an HP dc7100 P4 3Ghz box with an intel 915 Chipset. If I put in 2x512MB PC3200 DIMMS or 2x512MB and 2x256MB PC3200 DIMMS then it runs at DDR400 Dual Channel, but if I put in 4x512MB PC3200 DIMMS (when each pair runs at DDR400 on their own) then the system runs at DDR333.... Any ideas? Could it be that I'm using the onboard video at present which shares the RAM? I've not got a PCIe card to try yet.

What's better anyway 1.5GB at DDR400 or 2GB at DDR333?

Cheers,
Steve

[SteveC]

Oh should also add that if I put in 4x256MB PC3200 DIMMS then the system runs at DDR400 fine.

[az]

Could very well be that the board doesn't support DDR400 at more than 3 GB. If you're not using a 64 bit OS, then most memory over 3 GB can't be used anyway, so you might as well leave it at that. Whether 1.5 GB of (slightly) faster memory is better than 2 GB of slightly slower stuff depends on what you're doing. If you are using lots of programs or programs that shift large masses of data through RAM (a web browser with 20 open tabs full of pictures uses a lot of memory!) then more RAM is probably preferable. You probably won't notice the speed difference between the two RAM speeds without measuring it anyway.

[SteveC]

Sorry I've just read what I put up there and it's all wrong I'm out by 2x

4x256 works as does 2x512 and 2x256

4x512 is what doesn't work

[az]

Adjust my post for numbers then

[MultimediaMan]

The memory controller on I915 chipset is pretty good, but the way it works on the Pentium 4 platform, there is not a huge difference between DDR400 and DDR333. The the step down in RAM is a limitation of the I915 Chipset IIRC.

Athlon64s Socket 939s and Opterons are a different story because of the integrated memory controller and NUMA support. There is a marked performance difference between DDR333 and DDR400 on the Athlon64/Opteron Platform.

[SteveC]

I'll stick with the 4x512 for now then. I wonder could it be to do with 2 of the 512's are double sided and 2 are single sidesd. Maybe if I swapped out the double sided for proper HP (which is actually Micron) single sided 512's I'll be fine...

[Fat Tone]

No bios override?

[Admiral]

I'll stick with the 4x512 for now then. I wonder could it be to do with 2 of the 512's are double sided and 2 are single sidesd. Maybe if I swapped out the double sided for proper HP (which is actually Micron) single sided 512's I'll be fine...

That was my guess, mixed single sided and double sided modules. I'm also not sure if 4 single sided 512 modules would work, you may actually need 4 double sided. Normally these things are covered in the manual or on the manufacturer's site, since you have a HP system you'll probably have to dig for an answer or ask them directly.

[Technoid]

In this particular case i's probably a motherboard limitation,

Tho' I think you will notice the memory amount more than the memory speed.

[az]

And please don't buy HP branded memory modules if they are even a tiny bit cheaper than other brand-name modules. As you've said yourself, they're the same anyway.

Maybe your MB supports 3 GB RAM? I'd get 2 1 GB modules then and either run those alone and see if they get to DDR400, or use 3 GB (which is what I'd do).