Dual Channel DDR with 3 dimm slotts

[Freezybear]

I was reviewing some of Tom's Hardware's mother board articles, specifically the nforce2 b/c of the dual channel DDR. But I have a question: Dual channel means it has to be run together with another memory module right? Just like the dual channel rambus solutions. But how does this work with only 3 dimm slots? Shouldn't it be an even number?

 

[Crashman]

The nForce runs the two channels separately. Two DIMMs are on one and one on the other. For optimum performance exactly 2 modules should be used in exactly the right slots.

<font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>

 

[friendofp]

I was reading this same article and am a bit confused. It says that the nforce supports 2 DIMM@DDR333 Dual or 3 DIMM@DDR333 Single. How much of an advantage is there to running in dual mode assuming you don't need the extra ram the third stick of memory will provide you with?

Reality used to be a friend of mine!

 

[Crashman]

The article shows you the performance difference, 3 DIMMs should give you the same performance as 1 DIMM, look at the <A HREF="http://www6.tomshardware.com/mainboard/02q4/021111/nforce2-10.html" target="_new">BENCHMARKS</A> you'll see one board was tested in both single and dual channel modes.

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[wschuerm]

indeed diference is that in dual mode the bandwidth is doubled to 6,4 BG (on paper) with ddr 400 but as athlon xp (2600+ and over) only have a 333MHZ fsb it doesn't matter much anyway altough (not sure about this , i read it somewhere) with 2 sticks the controllers works like raid writing to one stick and preparing the other to be read from or to bewritten upon thus making the wait times as small as they can

Remember the time You used 20Mb harddrives

 

[Crashman]

Right, the only way you'll use more than 2100MB/s of bandwidth at standard bus speed is with a P4.

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[eden]

I think the test has proven Crash, that even Athlons benefit actually from Dual Channel, despite being OVER the limits. You always kept yelling at me at how DC helps nada when the bus is below the memory bandwidth, well look now! It seems enabling DC helps, and not the mem controller's efficiency!

--
*You can do anything you set your mind to man. -Eminem<P ID="edit"><FONT SIZE=-1><EM>Edited by Eden on 11/13/02 04:50 PM.</EM></FONT></P>

 

[Crashman]

Actually the bandwidth isn't helping, the nForce stagers the memory timing so you can get alternate read/rights, reducing latency.

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[MHolt85]

I just got a new Asus A7N8X with 2 PC3500 DDRAM of Kingston HyperX. The memory registers at 200 MHZ, but in SiSoft Sandra I'm only getting around 2050 MB/sec. My FSB is set to 133 (AMD XP 2400+), but I really don't understand the dual DDRAM feature.

 

[Elder]

MHolt85,

I'm no expert, but according to Asus' web site, that board only supports Max. 3 GB unbuffered PC3200/PC2700/PC2100/PC1600 non-ECC DDR RAM Memory.

So perhaps the motherboard is throttleing back your memory? I don't have an clue either. All this is greek to me. Been a few years since I paid attention to new tech.

In regards to dual channel and what not:

http://www.nvidia.com/view.asp?IO=feature_dualddr

http://www.nvidia.com/view.asp?IO=twinbank

Still waiting for my new case and el cheapo PC2700 ram to arrive before I can fire that bad boy up.

 

[MHolt85]

From what I know about this board, I called Asus support and they told me that the DDRAM Dimms have to be located in slot 2 & 3 (both blue sockets) - this was unclear in the manual. I'm running a total of 1 GB (PC3500 DDRAM). Running at 7-2-2-2T with the Memory Frequency set to SPD. When the memory frequency is set to sync this gives you the Dual channel DDR feature, but it limits you according to your FSB. Because I'm running a 2400 with a 266 FSB. My memory only runs at 133 MHZ in Dual channel (not oc). This is similar information in regards to a post above about AMDs not reaching the potential of Intel.

 

[Crashman]

It depends I guess on how they do writes. The only way I can see for them to do writes is too and from the CPU, but I'm sure someone else will speak up. And bandwidth to/from the CPU would be max 2100MB/s.

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[MHolt85]

Would this be why I can't obtain anything over 2050 MB/sec in Sandara? I know benchmark tests are not everything and AMD has complained in the past about how most benchmarking tests favor Intel.

 

[Crashman]

That would be my guess, your CPU hits a transfer wall at 2100MB/s so Sandra might not be able to check the memory beyond that speed. In fact, faster memory doesn't help the CPU with its increased bandwidth, it helps with its decreased latency.

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[numlok]

Hey MHolt85,

I'm super curious how this works out for you, as I just palced an order for the same MoBo and RAM (hadn't yet read this thread).

The first thing I thought when checking out all the new Dual-Channel DDR boards was, "That's weird... I wonder why they all have only three slots? Isn't that just going to screw with the Dual-Channel?". But seeing as how they're all (currently) set up this way, I had to bite the bullet (although I held off on purchasing the 3rd DIMM, until I learn more about this).

I do have a different CPU (XP 2800+), but will be following this thread vigilantly until I get the new system up and running (and beyond as well, I'm sure).

Please continue to keep us posted on anything you learn.

Cheers, and good luck!

num-