RAM Speeds

Sorry if this sounds dumb. A friend has a PC (P4 2GHzish, Packard Bell) which has a 256Mb DDR RAM PC2100 266MHz CL2.5, I have a spare 256MB DDR RAM PC2700 333MHz CL2.5. He has a spare RAM slot, you can see where this is leading. If I put my "faster" chip in, will it work OK? Will the system merely run the chip slower or will this cause problems. Also does it really need to be a "matched" pair? I can try it I guess, I also have a RAM testing program on CD-ROM the self-boots so I can leave that running for a while.

Thanks

It will run as fast as the slowest clocked ram.

thought so, OK well I'll try it out. I asked because in the "old days" sometimes newer RAM couldn't run at certain slower speed believe it or not.

I know. It is ok now providing it fits and you don't mix ram types.

Just be sure the slowest chip is in the first slot so when the BIOS detects the CAS latency of the RAM it detects the slower speed, else you'll be in for system hangs galore ;).

You only need matched pairs when doubling your FSB speed (2x400Mhz FSB), otherwise DIMM's are happy as individuals. The only other technical reason for matched pairs no longer applies (64bit addressing on a 32bit bus).

Huh? This makes pretty much no sense at all. FSB speed and matched DIMMs bear no relation to each other whatsoever. I don't even know what 'doubling your FSB speed' means, unless you're misunderstanding what DDR is.

DDR RAM does not need to be in matched pairs. Most modern chipsets (and of course AMD CPU's) can enable faster memory speeds by reading and writing 128 bits at a time if you have a matched pair of DIMMs (a single DIMM module transfers 64 bits per access).

heh, no I'm confused. btw, both chips were CL2.5 but I will leave the slowest in the first slot. We'll see what happens.

you only need matched pairs of dimms (and sometimes not even then) to use 'matched mode' on some amd systems, it gives a little speed boost to ram but isnt worth worrying about.

well just to throw a spanner in that theory, the reason I've got this 256MB chip is I bought it for someone's packard bell who had EXACTLY the same type of RAM (different manufacturer) but when both chips were in, the upper chip was getting memory errors (swapping them round only 256MB was detected). The chip was detected but windows kept crashing and a special memtest app revealed problems. I got them a matched pair and it worked fine, and the previously "duff" chip was able to be run as a 3rd one giving 768Mb RAM without errors, except I kept it in the end. Weird hunh?

Also I'm running my P4 3.2GHz with a matched pair and some special mode is set in the bios to make use of it, can't remember what it's called.

DDR ram is backwards compatible -- you can mix PC2700 and PC2100 just fine, they will both end up running at PC2100 speeds. Depending on the motherboard, you may need the slowest stick in your first RAM slot.

One catch: make sure you're not mixing DDR and DDR2 / DDR3, etc... The DDR2 / DDR3 run at a lower voltage than the standard DDR ram, and plugging a DDR2 chip in a DDR slot would fry them. (If they even fit, not sure about that) but since this is PC2700, it's more than likely regular DDR memory, so should be fine.

Cheerz, I basically thought it would be fine, but I like backup.

The only time you need matched pairs is in dual channel motherboards. The system will run without paired ram but you won't get the benefit of the dual channel speeds.

Bam. There ya go.

I have a dual channel motherboard and have enabled it in bios.