Mixing Different DDR2 Memory

I have a notebook with a DDR2 533MHz CL4 memory module and a spare DDR2 667MHz CL5 memory module. If I mix the DDR2 533MHz CL4 memory module with a DDR2 667MHz CL5 memory module will they both be forced to run at 533MHz CL5, which will mean the entire memory will be slower?

You are aware that your laptop uses SO-DIMM and not just DIMM right?
//Danne

IMO you will only run as fast as the slowest.

That’s the usual outcome.

Mixing memories will force the computer to default to the slowest ram speed. It’s usually not a good idea when you’re trying to run dual channel.

Thanks guys. :flower: That’s what I thought but I wasn’t sure the slower CAS Latency would override the other module as well.

The 667/CL5 module should be able to run at 533/CL4 timing as well. Trouble is you probably won’t be able to force it in a notebook BIOS. The cpu-z utility will show you what’s happening (maybe with the original 533/CL4 in slot #1 they’ll both run like that). :slight_smile:

Thanks, yes, that’s what I was hoping might happen, but the 667/CL5 module I have is sealed and even though it’s a hassle and a cost, I do have an option to exchange it.

It’s possible the module may have multiple timings, not sure if DDR2 works the same way, but I’ve seen PC3200 that has 3 timings, CL3 @ 200MHz, CL2.5 @ 166MHz & CL2 @ 133MHz.

Might get away with forcing 533/CL4 if you have manual timings, but the worst case would be the slowest of both speed & timings - if the module does have multiple timings, but they are not correctly recognized, then you may still need a manual setting option (often concealed in OEM BIOSes) in order to enforce the optimal settings

Yes DDR2 can have multiple timings. The supplier of the memory module has said to try it and see what happen, as they are all out of 533/CL4 sodimm anyway and don’t expect to get any more.

Cressida, thanks for reminding me about CPU-Z. I’ll check it out later today and see what it says before and after fitting the module. I’ll report back as to how I get on.

It all went well. The 667/CL5 module had a timing table entry for 533/CL4 and it was just selected by default. The only difference is a change in Tras from 11 to 12.

Here’s the CPU-Z screen shots, before and after:



Looks about right there. Glad [I]I[/I] could be of help for a change. :slight_smile:

wow…glad that worked out dandy for ya…most nice.