Mixing Different DDR2 Memory

vbimport

#1

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?


#2

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


#3

IMO you will only run as fast as the slowest.


#4

That’s the usual outcome.


#5

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.


#6

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


#7

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:


#8

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.


#9

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


#10

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.


#11

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:




#12

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


#13

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