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1 RAM Module -VS- 2 RAM Modules? Performance?

Posted on 2004-10-19
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Last Modified: 2013-11-10
I currently have 2 168-pin dimm slots, one of which is being used by a 256 MB DDR RAM module, therefore my total system memory is only 256 MB, and I have only one slot available.

I would like to upgrade to 512 MB.

My question is this:

Is performance affected when two RAM modules are installed? In other words, would my system achieve better performance by installing a single 512 MB RAM module, versus two 256 MB RAM modules? The cheaper solution is to just buy one 256 MB module, but what about performance?

Thank you for your time!
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Question by:techzzz
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by:Callandor
ID: 12351621
There is no difference in performance, unless you have a motherboard that supports dual-channel RAM.  Dual-channel RAM gives you perhaps another 10% improvement, but you also need matched RAM (speed, size, latency) in order to take advantage of this.  Otherwise, adding capacity in the future is a good reason for going with fewer sticks.
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by:TRobertson
ID: 12354211
If you get to the detail of comparing what performance changes you get from having two sticks vs one stick of memory you would probablly be dealing with higher performance memory sticks.  You must remember every stick of memory has individual charistics of speed, latency, and size.  You could buy two stick of memory of the same type and size from the same manufacturer and most likely they would perform differently if used independently.  Once could be faster than the other and one could be 5 to 10 MBs larger.  However higher performance memory (popular with gamers) can be purchased in pairs whereas the manufacture has selected two stick of memory with close to the same performance. (see link for example) and packaged the memory together.  So unless you are dealing with this type of memory most likely you will not see a significant difference by adding two stick of 256 vs one stick of 512.

http://www.newegg.com/app/ViewProductDesc.asp?description=20-144-324&depa=0
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by:mingtze
ID: 12354825
Hi,

2 sticks of RAM versus 1 stick will NOT affect performance except under the following situations :

Because all RAM modules need to run at the same speed settings -

1. The existing stick of ram has a higher DDR speed rating than the new stick. Both sticks would have to run at the same speed, so you might need to run them at the slower speed to avoid stability problems. For example, if you had a stick of (PC3200) DDR400 and bought a new stick of (PC2700) DDR333, you will most probably need to run them both at the slower common speed of DDR333.

2. The existing stick of ram has a higher CAS latency than the new stick. Similar to the above, but without going into too much technical detail, manufacturers give a CAS rating of 2, 2.5 or 3 to various models of their RAM, with 2 being the fastest. If your existing RAM was running at CAS 2 and you bought a new stick running at CAS 2.5 or 3, then both sticks will need to run at the slower common CAS latency setting.

3. Hardware limitation. Some motherboard manufacturers might (or might not) document in your user manual that running x number of modules might result in not running at the maximum performance. For example, some motherboards I know of (sorry cannot remember any examples offhand - but if you need I can dig them up for ya) support DDR400 speeds and provide 3 banks of RAM, but state that it can only run at DDR333 if you fill all 3 banks of RAM at once.

Chances are, for either case your motherboard by default should automatically detect the speeds accordingly and throttle down if needed.

The differences between the speed (whether DDR or CAS rating) of various RAM modules are not noticeable by the average user. You'd need to be a power user who knows the system performance like the back of your hand, or use a synthetic benchmark.

In general, even if you bought a slower stick of RAM, the performance slowdown would be offset by the feeling of faster system performance due to more memory available (512 of "slow" ram is typically faster than 256 of "fast" ram in an average Windows XP environment).

Hope to help.
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by:Gaud-wo
ID: 12356302
No doubt that most stated above is right, but if you aren't into getting every last drop out of your hardware, then: Yes, you can buy a 2nd 256MB stick. Or a 512MB and just add it.
Do check what kind of ram your current one is (should be printed on the side, like "PC2700" and "CAS2.5") - and look for the same type of ram when you buy it.

Cheers
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by:JoeJJohnsonII
ID: 12361670
Normally there wont be a difference. The only time that having two sticks of memory would increase performance is if you have a dual channel board with two identical sticks. Making sure that both sticks are as close to the same as possible will help in making sure that it runs more stable then having two different sticks becuase the motherboard is going to have to do some reconfiguring to make them match.

Honestly, if I were going to go and get a new stick of ram, I would sell the 256 stick to a friend or co-worker and go buy a new 512, low latency stick. I dont know what motherboard you have, so you need to find out if your board will support something like that. Heres a link to some PC3200: http://www.newegg.com/app/ViewProductDesc.asp?description=20-144-160&depa=1. You should get some performance boost from this. I dont know if you will be able to actually see the difference, but I was able to see it on my system.
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by:Gaud-wo
ID: 12367167
TRobertson: Can you give me your source on the difference in Ram capacity (5-10 MB), I've never heard of this?

FYI:
The main reason why you want to buy a pair, is because 2 blocks of 'same type' ram can look alike and have the same features, but contain newer revision chips that have -slightly- better performance. Latencies, size, manufacturer and product code may be the same, but that doesn't mean the chips are (like with NVidia's GeForce series - you can't tell if it has DDR1, DDR2 or DDR3 memory by the package!).

And in "dual pair" setups the manufacturer doesn't "select" some Ram blocks with close to the same performance. Ram is made in sheets of about 40*40cm / 16*16" (I could be off a bit here), the chips are soldered on, and dual pairs are just taken of the same sheet (so you're sure it's the same PCB and chips). There is -very- little difference in these pairs, as almost all features are identical.
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by:Gaud-wo
ID: 12714899
I think this information is relevant for future reference.

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