Need clarification.

[Guest]

I have been a steady visitor to Toms Hardware Guide for many years however, I have never posted a question/response here before.

Half of everything I know about computers I have learned from THG the other half from experience.

THG has given me knowledge, understanding and satisfaction. This is great!
That having been said I need clarification regarding a nForce 420 Mainboard and the 3 Dimm slots.

In a recent THG review of 13 Mainboards, I quote:

"But there are a few snags: The Nvidia chipset will only reach peak performance with two identical RAM modules. If, however, a third RAM module is added to the fray, the dual-channel mode, with its 128 bits of bandwidth, is automatically deactivated".

What does that specifically mean? What does the 128 bits of bandwith do? What would change if I put a 256mb PC2100 DDR Stick in that third slot along side 2-512mb PC2100 DDRs? on that MSI 420 nForce Board?

I would like to utilize that 3rd slot, however another 256mb of memory doesnt matter to me if it deactives an important dual channel benefit. What is the third slot good for then? Any insights?

Cheers.

 

[OldBear]

There is a reported problem with the nVida motherboards when all three Dimm slots are used. It takes a memory performance hit. At the present time only 2 slots can be used without this memory slow down and it varies between brands. Everyone is hoping for an updated BIOS that will fix the problem. This occurs with double sided memory sticks which most are. Right now the only fix is to slow the memory down.

<font color=blue>Remember.... You get what you pay for. All advice here is free.</font color=blue>

 

[Guest]

What does that specifically mean? What does the 128 bits of bandwith do? What would change if I put a 256mb PC2100 DDR Stick in that third slot along side 2-512mb PC2100 DDRs? on that MSI 420 nForce Board?

I would like to utilize that 3rd slot, however another 256mb of memory doesnt matter to me if it deactives an important dual channel benefit.
What is the third slot good for then?

 

[OldBear]

Here is some good info. <A HREF="http://www.gamepc.com/reviews/hardware_review.asp?review=nforceddr&page=1&mscssid=&tp=" target="_new">http://www.gamepc.com/reviews/hardware_review.asp?review=nforceddr&page=1&mscssid=&tp=</A>

<font color=blue>Remember.... You get what you pay for. All advice here is free.</font color=blue>

 

[Trainee]

Look at the bandwith as a water pipe: the greater the diameter of the pipe, the more water you can get going throug it. If you had to get 1,000 gallons of water from point A to point B, using a higher diameter pipe would get the job done faster (assuming everything else is the same-- constant transfer rate, etc.). The same thing aplies to memory. The greater the bandwith the greater the throuput-- once again, that is assuming everything else to be equal. So the real question is wether you are willing to sacrife higher efficiency in exchange for more physical memory. Quality vs. quantity.
I hope this helps.

 

[jclw]

Since the CPU uses 64bit access, and the GPU uses 64bit access, 128bit access allows both the CPU and GPU to access memory at the same time.

I think the 3rd slot becomes a problem because the northbridge actually has two 64bit memory controllers in it. The first one ("0") deals with slot 0 and is deisgned to mainly feed the CPU. The second one ("1") deals with slots 1 & 2, and feeds mainly the GPU. When they each have one identical DIMM, they can work simultaneously. But if one memory controller is dealing with two memory modules I think it throws the timing off.

- JW<P ID="edit"><FONT SIZE=-1><EM>Edited by JCLW on 12/14/01 03:54 PM.</EM></FONT></P>