Have a question/riddle for the memory gurus on this forum:

I have an Asus A7N8X with an Athlon XP 3000+, currently with 2 512mb DDR PC3200 (1 gig total) in dual channel mode. I have one slot left open.

Will I see more benefit from getting an identical 512mb memory module to fill slot 3, thus keeping dual channel mode on?

OR

filling slot 3 with a 1gb memory module?

Oh, filling slot 3 with the 1 gig memory module would turn off dual channel, from what I'm reading in the manual.

Uhhhh, dual = 2

This has been mentioned before but dual channel mode on a socket A system offers little or no benefit. This is because the max FSB (un-overclocked) on any socket A CPU is 200MHz/400FSB, which gives a CPU bandwidth of 3200MB/s. That 3200 should look familiar...PC3200 RAM running at 200MHz has a max bandwidth of 3200MB/s, so it's a perfect match. In dual channel mode, the theoretical RAM bandwidth jumps to 6400MB/s, but since the CPU limits the bandwidth to 3200MB/s, running dual mode does very little to boost performance.

If you have an extra 512MB stick, throw it in & run single channel, but if your 3000+ CPU is the 166MHz/333FSB version rather than the 200MHz/FSB version, clock your RAM at 166MHz to match. Again, there's no point running the RAM bus faster than the CPU bus. Double check these BIOS settings....

System Performance = User Defined
CPU Interface = Optimal
Memory Frequency = 100%
Memory Timing = Optimal
FSB Spread Spectrum = disabled
AGP Spread Spectrum = disabled
Graphics Aperture Size = 128MB
AGP Frequency = 66MHz

Uhh, yes, granted, 2 = dual, but strangely enough, the manual says putting in a 3rd identical memory module keeps it in dual channel mode. I'm not sure how this supposedly works out.

Thanks for the info on socket A and dual channel = minimal benefit. I think I saw this tested way back when the A7N8x was the latest, greatest thing ever.

I'm purchasing an Ultra 1gig module from Radioshack... <$50 with rebates. Hopefully will keep me puttering along for a while longer before I have to upgrade my system.

So what was even the point for dual channel mode on Socket-A is my question? I never got that either.

More of a sales pitch then a preformance pitch?

AMD Athlon 64 X2 4200+
2GB Dual Channel DDR 3200
Nvidia 6800GT
SATA II 250gig 7200rpm 8mb cache
Gigabyte Nforce 4 SLI

So jam, if the Athlon 64 3000+ s939 processor has 9600mb of max bandwidth then that means the only ram that can max out that high in dual channel mode would be DDR 600 (4800)?

I haven't came across any motherboards on a s939 that can support DDR 600......

AMD Athlon 64 X2 4200+
2GB Dual Channel DDR 3200
Nvidia 6800GT
SATA II 250gig 7200rpm 8mb cache
Gigabyte Nforce 4 SLI

Sorry, I read it wrong it's up to 6.4gb max bandwidth so dual channel mode on athlon 64's would make perfect sense with DDR 400.

AMD Athlon 64 X2 4200+
2GB Dual Channel DDR 3200
Nvidia 6800GT
SATA II 250gig 7200rpm 8mb cache
Gigabyte Nforce 4 SLI

"So what was even the point for dual channel mode on Socket-A is my question?"

"More of a sales pitch then a preformance pitch?"

Exactly. Intel was doing it, but their systems could actually take advantage of it...basically, AMD "had" to do it to keep up, even though it offered minimal advantages on the socket A.

http://www.sudhian.com/showdocs.cfm?aid=480&pid=1769

The A64 is a completely different animal. The CPU communicates directly with the RAM thru the onboard memory controller which is "officially" designed for 6.4GB/s bandwidth...as you said, DDR400 x 2. The official JEDEC standard is DDR400, anything higher than that (DDR500, DDR600, etc) isn't "official" & can't be "offically" supported. Even if the memory bus is capable of more than 6.4GB/s (which it is), AMD can't "officially" say that.

I wonder what the new AMD 64 X2's max bandwidth would be on the AM2?

Where can you find a listings of each processors max bandwidth instead of having to google all over for each processor?

AMD Athlon 64 X2 4200+
2GB Dual Channel DDR 3200
Nvidia 6800GT
SATA II 250gig 7200rpm 8mb cache
Gigabyte Nforce 4 SLI