Dual Mode Memory

Factual Questions
1

I’m upgrading a PC I built in 2006. Supermicro P8SGA supports Pentium 4 and uses the Intel 915G chipset.
here’s the one page data sheet
http://www.supermicro.com/products/motherboard/P4/915/P8SGA.cfm

It supports Up to 4GB dual channel unbuffered, non-ECC DDR 400/333 SDRAM

It’s been awhile since I researched dual channel memory. I know it routes the memory through two pipes. You have to buy matched pairs. I Always get Kingston. They sell it in matched pairs.

Doesn’t it also cut the actual memory to the OS in half? Right now I have two 512MB modules running dual. A Gig of physical memory. Isn’t that really only 512MB that the OS sees?

I’m upgrading the PC from Win 2000 to Win7 and I know 1 Gig is the minimum. 2 Gig desirable for Win7. I plan to buy 4 1GB modules and that maxs out the motherboard. So, in Dual mode that would really be 2 Gig memory for the OS?

I’ve been trying to confirm this. For some reason my google fu is letting me down.

Am I remembering correctly? Dual Mode Memory cuts it in half? A MB with Three channel memory would cut it by 2/3?

or not? I just can’t remember where I read this.

2

You have access to the full amount of memory you stick in. Duel memory mode just has to do with alternating the memory access between the sticks. One is being read when the other is being written.

1G + 1G = 2G for your system OS minus any reserved for an on board graphics card.

3

Win7 64 bit requires more memory for operations than Win7 32 bit because of the size of the addressing. In my example you would still see 2G available for the OS regardless of which you used, but the 64 bit will use more for it’s processes. This may be where your thinking the memory is halved comes from.

4

thanks. I’ll rethink buying 4 1GB modules.

really all I need is 2 1 GB modules along with the 2 512k I already have installed.
That gives me 3 GB. Plenty for Win7 in 32 bit.

5

If anyone wants to find out if they are running Dual mode memory a free proggie will tell you.
It also tells you a lot about your cpu. The type, speed, instructions it supports etc.

http://www.cpuid.com/softwares/cpu-z.html