Should I get more RAM?

[Skillian]

Slightly theoretical question this one as my pay packet this month is going on a Hyundai L90D+ monitor, but anyway...

I currently have 2 sticks of 256MB PC3200 RAm running in dual channel, but I'm finding it being eaten away with background programs etc. I'm also seeing a lot of hard disk access when I'm playing newer games like HL2.

I think more RAM would help this, but I can only afford to buy 1 stcik of 512MB - this means I wouldn't be running in dual channel anymore (256 + 256 + 512).

So my question is how much performance would I lose going to single channel, and would this "upgrade" actually make my system slower?

edit: Specs:

MSI Delta L mobo
Barton 2500+ oced to 3000+
9800 Pro
2 x 256 PC3200
etc. etc.

[Snee]

You can still run in dual channel using the two 256 sticks :unsure: I think.

And I don't think it'd make you noticeably slower running anything, and you should see a performance boost when you are running something memory intensive, for sure.

EDits: the two sticks now running dual chan have to be next to each other.

So put them in the first two slots and the 512 stick in the third (or fourth if you have one).


More... I don't know about your mobo but in other cases I know that the first pair of dimm slots had a separate memory controller and the other pair or single slot had another, so for it all to run in dual chan you'd put the 2 256 mems on the first controller and the 512 stick on the other, that way you had the same amount on both controllers and could run it all in dual channel, theoretically.

Not sure if it worked with a different brand of RAM on the other controller, but at any rate it was possible to run the first two sticks in dual chan on those systems, together with a third stick.

[Made more sense of it by adding the words in bold.]

[Spicker]

You can still run in dual channel with the two 256 sticks :unsure: I think.

No you can't....unfortunately :( you need even number of sticks

i added a 128mb stick to my dual channel 256x2 and its actually slower, bandwith wise but im sure if u add 512 you should see a big difference :01:

[Skillian]

OK i put this in another forum too and got a similar answer about how i might still be able to run dual channel with three sticks (256 + 256) + 512, which is effectively 512 + 512.

And I have 3 memory slots on my mobo - 2 purple and 1 green, so it looks like it might be possible with the 2 x 256s in the purple and the 512 in the green.

Guess I need to find some specific info on my mobo...

[Snee]

No you can't....unfortunately :( you need even number of sticks

i added a 128mb stick to my dual channel 256x2 and its actually slower, bandwith wise but im sure if u add 512 you should see a big difference :01:
Just googled it and I don't think these guys (http://www.nforcershq.com/forum/viewtopic.php?t=44570&postdays=0&postorder=asc&start=0) would agree with you. For instance.

Based on this article (http://www.digit-life.com/articles2/nforce2-1vs2channels/?98399).

EDit: I had it the wrong way around tho', it's the first stick that should be the same size as the other two together.

EDitII: the reason yours can't work is pretty obvious.
256+256 doesn't equal 128, you know.

EDitIII: Skillian, it definitely sounds as if your mobo allows for it, what with them having marked out which slot belongs to which controller and all.

[Skillian]

Thank you guys, especially SnnY.

MSI forums confirm I can run three sticks in dual channel, as long as the two sticks on the first memory controller have the same combined capacity of the stick in the second.

I guess I could have checked there first, but I had no idea it was possible. Good news for me :)

[Snee]

Cool :)


EDit: glad you made sense of that, as I feel slightly wreckered and managed to confuse myself when I wrote it. :blink: :lol:

[Izagaia]

Newbie question (please be gentle) :


What is "dual channel" so far as RAM is concerned? And if there is some sort of performance boost or notable benefit in running it, how do you do so?

[Snee]

How Dual Channel DDR works

Dual Channel DDR works by giving the north bridge two independent controllers to access two sets of memory. To put things in simpler terms, think of a stick of DDR as a two way bridge. DDR achieves double the data rate of normal SDR memory by allowing an independent data path for upstream and downstream travel; much like how a bridge or road works. The theoretical maximum amount of bandwidth for a stick of DDR400 is 3.2GB per second. Like a bridge with a speed limit, the amount of throughput achieved varies depending on the type of data it deals with.

With Dual Channel DDR, the data path is doubled once again by using two sticks of DDR memory. By giving the CPU/north bridge another data path to the memory, bandwidth is effectively doubled, giving Dual Channel DDR400 6.4GB/s. In simple terms, think of DCDDR as widening the bridge by adding two more lanes. This effectively allows more data to travel faster; much like traffic moving faster when there’re more lanes to drive in. The downside to this is traditional DCDDR solutions require pairs of same sizes.

In more technical terms, DDR memory is 64bit and communicates with the CPU/north bridge at 64bit. Dual Channel DDR can operate in two modes. One mode is it accesses the memory in 128bit mode, which is how most DCDDR chipsets operate. The other mode is it communicates with the two memory controllers in 2x64bit mode, treating each controller individually.



source (http://www.sis.com/support/learn/techarticle/dualchannel.htm)

Basically it can double the bandwith at which the memory is accessed by when treating them as a unit, or it can access modules independently in a more effective way than on non-dc systems.

It requires them to be matched as described in this thread tho'.

Exactly how big a noticeable gain you get by running your memory modules in dc I can't tell you as there appears to be different results for different tests. It'll give you summat faster access times tho', this is without a doubt.

[BILLY-THE-FISH]

Sorry to hijack thread... but i have a Ram question too

Sorry its a bit noob, I want to install another 512Mb of Ram in my motherboard (Asus P4S533-E) but not sure which slot to put my extra (with 512 I have got at the moment) Ram in? I have no motherboard Manual and can't seem to find out on web anywhere. Does it matter which of the other slots (out of the 2 spare) I put it in?

Cheers

[lynx]

All this theory is brilliant, but in practice it usually means almost nothing for AMD processors.

Dual channel is fine in theory, it should give you a data path which is 128 bits wide. Except that your pci bus isn't 128 bits wide, the AGP bus isn't 128 bits wide, and the bus to most AMD processors isn't 128 bits wide (Athlon 64 Socket 939 is the exception).

So you've got a 128 bit data bus to your memory controller, and damn all good it will do you because the widest link to other system components is only 64 bits, except for memory to memory transfers. It is possible to devise tests which will show high bandwidth figures, but these are artificial and in practice the theoretical 6.4GB/s bandwidth is nowhere near attainable.

This is one area where Intel chips are getting better performance over AMD chips, because although they still only have a 64 bit bus, by having an 800MHz FSB speed they can take data twice as fast from the memory controller.

[Virtualbody1234]

... my motherboard ...(Asus P4S533-E) but ... I have no motherboard Manual and can't seem to find out on web anywhere.
http://www.asus.com.tw/pub/ASUS/mb/sock478/p4s533-e/e1034_p4s533-e.pdf

[bigdawgfoxx]

So what are the qualifications exactly. I have a dual channel setup right now...256X2 PC3200 2-2-2-5. If I were to buy another 512 stick for the 3rd slot, what would have to be the same to make it work? Just the PC3200 or the timings also?

[BILLY-THE-FISH]

http://www.asus.com.tw/pub/ASUS/mb/sock478/p4s533-e/e1034_p4s533-e.pdf
Cheers mate!! :w00t:

[Snee]

All this theory is brilliant, but in practice it usually means almost nothing for AMD processors.

Dual channel is fine in theory, it should give you a data path which is 128 bits wide. Except that your pci bus isn't 128 bits wide, the AGP bus isn't 128 bits wide, and the bus to most AMD processors isn't 128 bits wide (Athlon 64 Socket 939 is the exception).

So you've got a 128 bit data bus to your memory controller, and damn all good it will do you because the widest link to other system components is only 64 bits, except for memory to memory transfers. It is possible to devise tests which will show high bandwidth figures, but these are artificial and in practice the theoretical 6.4GB/s bandwidth is nowhere near attainable.

This is one area where Intel chips are getting better performance over AMD chips, because although they still only have a 64 bit bus, by having an 800MHz FSB speed they can take data twice as fast from the memory controller.

I've seen a couple of benchmarks where they got a whopping :rolleyes: 6% gain in overall performance with dual channel enabled, but most benchmarks only show how much faster your memory becomes and nothing about what you actually gain.

I think you might get something out of it tho', but you get a bigger boost from enabling 4 bank interleaving if you haven't, for instance. If that's an option on your mobo.

[Snee]

So what are the qualifications exactly. I have a dual channel setup right now...256X2 PC3200 2-2-2-5. If I were to buy another 512 stick for the 3rd slot, what would have to be the same to make it work? Just the PC3200 or the timings also?
According to one of those links I posted ( ! (http://www.digit-life.com/articles2/nforce2-1vs2channels/?98399) ) "the speed characteristics" should be the same.

Otherwise it gets slowed down to the level of the slowest stick. But that's when talking about the clockfrequenzy.

I think, tho', that it's the same thing with the memory timings, if they are set to auto. Otherwise, if you've tweaked them, you should watch out for instabilities if the new stick can't handle the timings set for the other sticks.

So for it to be totally stable, my theory is that the timings must be set to something the slowest chip can handle.

[Skillian]

Well the extra stick went in fine, and it all works in dual channel.

Used the same Crucial memory, same timings.