Adding SDRAM DDR

[yalamo]

A simple question for a memory guru:

I want to add SDRAM DDR. I ran SIW and it tells we that I have 256 MB chips in slots 1 and 2, with a speed of PC3200 (200 MHz). Does this mean I can safely buy and install a 400 MHz 512 MB DDR chip? (I have 4 DIMM sockets on my MB.)

 

[wahnula]

Not an anything guru here, but the question is how much memory can your mainboard support and at what speed? If you mix speeds all modules will run at the lowest module speed. If you have dual-channel memory it gets stickier, as those pairs nust match exactly.

Check your system at

http://www.crucial.com

and see what it tells you about your mainboard.

Tony

 

[yalamo]

wahnula, thanks. I should have made this clearer. My MB has 4 184 pin DIMM sockets (2 of which I'm already using); it supports DDR 400, DDR 333, and DDR 266, and up to 4 GB of system memory. If I understand DDR nomenclature, a speed of 200 MHz means that the memories are read at a clock rate of 400 MHz. I would just like to get some confirmation that I'm interpeting this correctly before I go out and buy more RAM.

 

[paparazi]

Yes indeed, PC3200 is DDR400 and by the looks of things this would mean that a 512mb stick of PC3200 would be compatible with the other two 256 modules.
This would however mean you loosing dual channel status if you motherboard supports it.
I would however like it if you could post more info on your setup.
CPU, Motherboard etc

We like members to GIVE and not just TAKE.
Participate and help others.

 

[yalamo]

paparazi, you've raised a point that I hadn't thought of, so thank you. I have an Intel D865GBF mother board. Right now I have two 256MB DDR sticks in DIMM's 0 and 1 in Channel A. Looking at the MB specs, it seems that I have a single channel configuration with dynamic mode

I see that if I put a 512MB stick in DIMM 0 (or 1) of Channel B, I will have a single channel configuration without dynamc mode. Practically speaking, what does this mean? I assume that the optimal configuration would be dual channel with dynamc mode, but what's the penalty in read or write speed to memory if I don't have the optimal configuration?

 

[wahnula]

yalamo,

Your best throughput will be by adding 2 x 256 MB matching sticks in your remaining slots. There is a good reference chart on page 25 here:

ftp://download.intel.com/design/motherbd/bf/C3263401.pdf

You should have your matching sticks on DIMM 0 of Channel A&B.

If you want to add another, non-matching stick you can have dual channel without dynamic mode. What does it mean in the real world?

The advantages of dual channel vs. single channel are negligible, but if your board is capable and you have the hardware might as well use the feature. Every opportunity to maximize speed (even a hair) should be taken! That's my M.O.

Tony

 

[cdogg]

The advantages of dual channel vs. single channel are negligible...

This is not necessarily true. If I setup four different chipsets with four different CPUs, you would see that all four would have a different dependency or reaction to dual-channel. Therefore, the answer to how much it matters heavily depends on the CPU and chipset architecture involved.

For example, the older Athlon XP (Barton) CPUs that ran on a 400MHz FSB (200MHz x 2) was one of the first to go through the test of "dual-channel". It was determined early on that dual-channel wasn't that much of a factor for this CPU, regardless of the chipset used. Most gains were only about a 5% increase over single-channel. The result here made sense, since dual-channel 400MHz DDR gave a jump in bandwidth to 800MHz. That does you no good if your FSB is only able to pace itself at 400MHz.

Dual-channel became more of a factor though later on as we saw FSB speeds increase. AMD's Athlon 64/X2, as another example, introduced Hypertransport which replaced the old FSB architecture and was capable of speeds over 1GHz. Here, dual-channel DDR became crucial to getting good overall performance. Intel's Northwood Pentium 4 took it to the 800MHz FSB threshold and beyond (Conroe is at 1066MHz), also shedding light on dual-channel importance.

So again, the bottom line is the CPU, FSB and chipset. We'd have to know exactly what CPU is involved here to make any kind of guess as to how important it is for yalamo. If the CPU supports an 800MHz FSB, then you're going to want dual-channel to keep the memory bus in synch.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[yalamo]

OK, wahnula and cdogg, I'm getting there. My processor is a Pentium 4, 2.6 GHz, and I see that I should add two 256MB memory sticks for the best configuration.

Which still leaves me with part of my original question. As I said, I ran SIW and it tells we that I have 256 MB chips with a speed of PC3200 (200 MHz). I thought that this means that I can use 400 MHz DDR's, but I ran across this reference:

http://www.kingston.com/newtech/MKF_520DDRwhitepaper.pdf

It says "In 2002, standard SDRAM began to be replaced with the faster Double Data Rate (DDR) SDRAM memory technology. DDR memory started with 200MHz DDR (or DDR200) and is now available in DDR266, DDR333, and DDR400 speeds for mainstream PCs."

Does this mean that the DDR's I have read memory at a 400 MHz rate, and I should get 400 MHz DDR's (since a 200 MHz speed DDR reads on both rise and fall of the clock)? Or that I have really old memory chips, and there's no point in getting anything as good as 400 MHz, and I may as well get 266 MHz DDR's, which is the lowest speed I can find?

 

[cdogg]

Nope, you've got the right type already. PC3200 is DDR400. When DDR SDRAM first came out, it was PC1600 a.k.a DDR200.

The speed rating gets confusing. PC1600 ran on a 100MHz memory bus, but since all DDR sends data on the rise and fall of the signal, it is labeled as the equavalent of 200MHz. So even though SIW is telling you that your memory is running at 200MHz, it's talking about the memory bus. It is not taking into consideration that the theoretical speed is actually 400MHz.


~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[yalamo]

cdogg, thank you very much, You're right, the speed ratings are confusing, but now you have cleared everything up for me.