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533 (PC2 4200) or 400 (PC2 3200) for i6000? - Page 2

post #21 of 25
6/29/05 at 12:27pm
The link below contains benchmarks that were done to prove that DDR2-533 gives higher memory bandwidth then DDR2-400 in an Inspiron 6000. This person compares DDR2-400 vs. DDR2-533 in dual channel configurations, and non dual channel configurations.

http://forum.notebookreview.com/showthread.php?t=13314
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post #22 of 25
6/29/05 at 1:24pm
Thread Starter 
ok so what if i run my machine with one 512 stick at 400mhz and one 512 stick at 533mhz. is this bad? will it work ok or what? thanks a lot.
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post #23 of 25
6/29/05 at 1:36pm
They'll both run at 400MHz, and you'll be OK. My desktop whitebox will dual channel dissimilar speeds of RAM at the lowest common denominator, but I don't know if all memory controllers will do this. You may or may not get them to operate in dual channel.
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post #24 of 25
6/29/05 at 1:40pm
When you mix DIMM's of two different speeds, the chipset defaults to the SPD settings on the slower dimm, in ur case 100mhz x 4 = 400mhz effective. dual channel will work but at the slower speed.

For most computers, synchronous operation is desired between memory and the cpu since data is fed to the chipset from the memory as fast as from the chipset to the cpu. There's no scheduling delay issues. I do not know the toll of having asynchronous operation on the 915pm chipset but it didn't matter a great deal for the first generation centrino chipsets with quadpumped 100mhz fsb paired with 133mhz and 166mhz ddr.

As for dual channel, the only use of the extra memory bandwidth is to offload direct memory access (DMA) devices such as hard drives and many pci peripherals. The gains are extremely small since dothan is pretty efficient when getting data from the memory and leaving memory bandwidth available for dma devices.
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post #25 of 25
6/29/05 at 2:41pm
Quote:
Originally Posted by Brett VanKirk
The link below contains benchmarks that were done to prove that DDR2-533 gives higher memory bandwidth then DDR2-400 in an Inspiron 6000. This person compares DDR2-400 vs. DDR2-533 in dual channel configurations, and non dual channel configurations.

http://forum.notebookreview.com/showthread.php?t=13314
Yes, I remember reading this thread a while back. This is the most important observation: 1xDDR2-533 = 2xDDR2-533 = 2xDDR2-400 > 1xDDR2-400

As long as one is using Dual-Channel mode, the bus is fully saturated with either PC2-4200 or PC2-3200, so 533MHz memory is no faster in this case.

However, when only ONE stick of RAM is present, the PC2-4200 will give ~10% increase over PC2-3200.

So for the person who originally started the thread, you can get either PC2-4200 or PC2-3200 memory to supplement the memory you already have. Once dual-channel mode is activated, your laptop will have maximum memory performance.

For those of us who have 2xPC2-3200 memory, there is absolutely no benefit in swapping for 2xPC2-4200 memory.

Cheers!

Jay
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