WinXP 32-bit and 4GB RAM - does it ruin dual channel?

[MichaelD]

MODS: If I put this in the wrong place, please move

RAM is so cheap these days that I'm considering buying another 2GB for 4GB, total.

I know in order to run dual channel effectively, you need the same size sticks. 4x1GB=4GB, but WinXP32 will only see 3.2GB approx. So that's like losing...80% of 1 stick, which throws the whole "equal amounts of RAM on each channel for dual channel" equation into a tizzy.

Will this skew the advantages you get by going dual channel in the first place?

 

[Gillbot]

Yes, I had 4GB in dual channel but you won't see much benefit from it. I got better performance from running 3GB in dual channel using 2x1GB and 2x512MB.

 

[MichaelD]

Thanks much, Gillbot. A question: I know that if you use different size sticks in dual channel, you get a POST message to the effect of "Dual channel running in compatability mode" or "Dual channel not optimized" or something like that. Did you have that problem when you ran mixed size sticks? I had not considered getting a 2x512MB kit for 3GB total...

 

[Peter]

The "vanishing" of the RAM is not done inside the RAM controller unit, but before the access even gets there. The RAM controller's operation does not change when some of its work is invisible.

So the answer to the original question is: The RAM controller is initialized to 2x2GB, and something higher up in the chipset's address mapping heirarchy is masking some of it.

 

[Gillbot]

Originally posted by: MichaelD
Thanks much, Gillbot. A question: I know that if you use different size sticks in dual channel, you get a POST message to the effect of "Dual channel running in compatability mode" or "Dual channel not optimized" or something like that. Did you have that problem when you ran mixed size sticks? I had not considered getting a 2x512MB kit for 3GB total...

No POST messages when I used mixed modules at all. It just came up as DDR Dual Channel, 3GB or something like that. I forget the POST message exactly.

 

[buddhatb]

Originally posted by: Peter
So the answer to the original question is: The RAM controller is initialized to 2x2GB, and something higher up in the chipset's address mapping heirarchy is masking some of it.

So does that mean the 4GB is operating in dual channel mode but system does not access/use it all?

 

[VirtualLarry]

Originally posted by: buddhatb

Originally posted by: Peter
So the answer to the original question is: The RAM controller is initialized to 2x2GB, and something higher up in the chipset's address mapping heirarchy is masking some of it.

So does that mean the 4GB is operating in dual channel mode but system does not access/use it all?

Correct.