# RAM not up to speed [Solved]

## alienjon

My desktop has an ABIT nForce4 KN8 Ultra motherboard with 1gb 400 DDR2 RAM (Corsair).  Recently, my roomate got some new parts for his compy and offered his old RAM to me (2x512mb 400 DDR2 RAM (OCZ).  I installed the 2 new 512 sticks and the motherboard reads them fine, but upon bootup it reports that they are only running at 200 speed.  I looked around google and discovered that if the RAM is running dual channel, then the speed is split between each channel (bi-directional: so it would be read as 200 speed for each direction (but is realistically 400)).  That's all fine and dandy, except that I'm currently running single-channel (because all 3 sticks are in).  Any thoughts as to why this might be?Last edited by alienjon on Tue Mar 16, 2010 12:19 am; edited 1 time in total

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## matze_na

I'm not exactly up to date on hardware specs, but at least for DDR (not 2) I remember that 400 is the effective clock speed or something, while the actual clock is 200. I guess that's where "Double Data Rate" comes from. This has absolutely nothing at all to do with single or dual channel.

If you change your setup to be able to use dual channel, you will get more speed out of it, but that won't change the clock of the RAM modules.

And, by the way, concluding from the link to your motherboard, your RAM is DDR, not DDR2. Since I own a motherboard with nforce4 chip and S939 myself, I'm pretty certain that's correct.

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## alienjon

You're correct.  DDR2, thanks.  Might this mean that the 200 is really the 400?  Also, as you have a similar motherboard, I believe I read in the manual that dual channel works only with pairs of RAM (2 or 4 chips).  Is this correct, or is there a setting I could configure to enable it?  (I didn't see anything in the BIOS, if it's there)

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## matze_na

Yes, I'm pretty sure your RAM is running at what is called DDR-400 which means an actual clock speed of 200 MHz. So everything seems to be okay there.

As far as I know, there's no way dual channel can work with an odd number of RAM modules. I'm not even sure if it will work with a 1 GB and a 512 MB module. All you can do is try that configuration out, if it works you're lucky and it might be your best option besides buying extra RAM.

Given that 1 GB + 512 MB doesn't work in dual channel, I guess you should just use your system as is, with a total of 2 GB RAM but only single channel.

Alternatives would be to either throw out the 1 GB module and go for 2x 512 MB in dual channel, or to buy some extra RAM, for 2x 1 GB or 4x 512 MB or whatever.

There's also definitely no option in BIOS to enable dual channel per se, if the BIOS thinks your setup of RAM modules supports dual channel, it will use it, and if it doesn't, there's just no way you could force it since it just won't work.

Try 1 GB + 512 MB just to be sure, but I don't think it'll work in dual channel. If it does, I'd say go with that. If it doesn't, go with 2 GB total and single channel.

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## Mad Merlin

Generally, you need an even number of identical sticks of RAM to run in dual channel mode.

Having said that, I don't know if you'll notice the difference in speed between single and dual channel RAM configurations, perhaps you should benchmark something relevant to you with 2x512M in dual channel vs 2x512M + 1G in single channel. On the other hand, you are likely to notice a speed boost with the extra gig of ram, even if it only gets used for file cache.

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## alienjon

matze_na, thanks for the explanations.  That clarified stuff for me very well!  I thought about trying the 1 + 512 configuration, but I daresay I feel more comfortable with the solid 2gb installed (even with a potential speed hit).  I've already noticed an improvement where I didn't know I had an issue!  Just to clarify, though, if I were to purchase another 1gb stick and install it parallel to the current 1gb stick, (the 512's would be paired and the 1's would be paired) then it should get dual channel then?  Or is it still hit-or-miss?

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## alienjon

 *Quote:*   

> perhaps you should benchmark something relevant to you with 2x512M in dual channel vs 2x512M + 1G in single channel

 

If I find the time to try out the 2x512 + 1x1 vs 1x512 + 1x1, how would I best benchmark the RAM?  The usual suspects? (top, free, mem, dmidecode, etc...?)

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## Mad Merlin

 *alienjon wrote:*   

> Just to clarify, though, if I were to purchase another 1gb stick and install it parallel to the current 1gb stick, (the 512's would be paired and the 1's would be paired) then it should get dual channel then?  Or is it still hit-or-miss?

 

Some motherboards may support that while others may not, I'm not sure the situation for your specific board. However, bear in mind that motherboards of that vintage (NForce 4) generally can only run at DDR 333 speeds instead of DDR 400 with all 4 RAM slots populated.

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## Mad Merlin

 *alienjon wrote:*   

>  *Quote:*   perhaps you should benchmark something relevant to you with 2x512M in dual channel vs 2x512M + 1G in single channel 
> 
> If I find the time to try out the 2x512 + 1x1 vs 1x512 + 1x1, how would I best benchmark the RAM?  The usual suspects? (top, free, mem, dmidecode, etc...?)

 

I wouldn't suggest any of those for benchmarking the speed impact of single/dual channel RAM, they would only confirm what you already know (how much memory you have installed). I was thinking more along the lines of something compute intensive, like compiling or playing games and measuring time/fps.

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## alienjon

I was reading through the manual when I installed them and I don't think that's the case (it certainly had 333 listed, but I'm fairly positive the 400 was there too).  I suppose that if I wanted to be really picky on this I'd just upgrade everything.  If only time and money allowed   :Razz: 

**Update**

 *Quote:*   

> I wouldn't suggest any of those for benchmarking the speed impact of single/dual channel RAM, they would only confirm what you already know (how much memory you have installed). I was thinking more along the lines of something compute intensive, like compiling or playing games and measuring time/fps.

 

Gotcha.  Thanks  :Smile: 

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