Memory question, single or double channel?

[Feek]

Is this me being a n00blet or is it telling me my memory is running in single channel mode?



Presumably this is because I have 3 x 1Gb strips of RAM installed due to motherboard limitations as it's a crap board?

The older version of CPU-Z said 'double' there

[Mark]

No, you're not being a n00blet. Memory has to be in pairs (each of the pair being the same size) for dual channel mode to work, so there's no possible combination that would result in 3GB running in dual channel mode.

[Feek]

Hmmm

I'm now pondering the implications and performance difference of having 3Gb of single channel compared to 2Gb of dual channel.

(btw, 2 x 1Gb and 2 x 512Mb would give 3Gb, so a combination is possible )

[Mark]

You're correct on 3GB. I blame the fact that it's 11.51PM.

Are you typically using more than about 1.5GB? If not, then it's an easy decision.

[Stan_Lite]

I am currently running 2 Windows Folding clients plus 1 linux SMP client (running in VMWare), Windows media player and Firefox open with 7 tabs and I'm using around 1300Mb of RAM (all 4 cores of my CPU are pretty much maxed out ).

I don't know how much RAM you typically use Feek but I'd be surprised if you maxed out 2Gb at any point.

I would imagine that the extra speed from dual channel would more than offset the loss of 1Gb in single channel.

[Mark]

Feek runs Vista, which automatically uses more memory.

But then again, I can (and do) quite happily run a Vista VMWare image inside Vista (don't ask why ), as well as the ubiquotous Folding@home client, and still have plenty of change from 2GB and no noticeable performance issues.

Suck it and see, I guess.

[Stan_Lite]

Originally Posted by Mark

Feek runs Vista, which automatically uses more memory.

So do I

[killerkebab]

I would have always said - more memory is better than faster memory.
That being said, there has to be a point where you have so much memory sacrificing space for speed is a better option.

[Feek]

I ripped one stick out last night before I went to bed but was so tired that I crashed before testing it. This morning I've checked and I'm now running in dual mode and my Windows Performance Index doofer thingie has gone from 5.0 to 5.5 on memory so that's a 10% increase in speed.

I suspect I don't _need_ the extra memory but it'd be nice to have it there. I paid for it, I may as well use it!

I'm going to look at replacing the motherboard. It's crap.

[Garp]

You'll find it hard to find any mobo that'll let you use 3Gb in Dual Channel mode, you need matching pairs to ever get it, e.g. 2x1Gb and 2x512Mb.

We have so much fun at work trying to explain the concept of "Matching" pairs to HP whenever we get a memory failure in a server. They'll send out any ol' brand, oftentimes not even the same timing and expect it to work (they have just one product code for DDR PC3200 512Mb of RAM , one for DDR2 4200 512Mb of RAM and so on, irrespective of timing, mfg etc. etc.) Whenever they send the wrong brand you can almost guarantee you'll struggle to get the server to boot properly, let alone go in Dual Channel mode.

Typical boosts from Dual Channel vary depending on mobo, speed of RAM, application, and so on, but you should see anything from 10 - 20% boost to any memory read / write aspect.

Originally Posted by killerkebab

I would have always said - more memory is better than faster memory.
That being said, there has to be a point where you have so much memory sacrificing space for speed is a better option.

Sadly thats not true. Virtually all operations require some transaction between your processor and your system RAM. You will always see a benefit from having faster memory access one way or another, unless you have so little your system is routinely paging out to the swap file. Under those circumstances the limiting factor is your hard drive speed and additional ram will make a huge difference. Bear in mind however, XP is fond of paging out to the swap file information it knows is being very static and not accessed often, its rare to find any windows box that isn't using its page file to some extent (Right at this moment on my 1Gb box I've got 600Mb free, but its using 200Mb Swap) The performance boost of Dual Channel is nothing to be sniffed about when memory is such a core part of almost all processes.