Dual Channel

I hear that I have to use two memory sticks that are exactly the same (make, design, code, etc.) or that come together when I use a dual channel mobo. But if I have four slots total, can I use two of OCZ (for example) and two of some other company, as long as they're in the right slots??

Or do I have to have EVERYTHING (memory sticks) identical?

 

Everything identical,you can try it you may get lucky,but if it doesnt work you then have the problem of returning the memory,if you can purchase the memory from a store and return it personally providing the store have a favourable return policy if you buy the memory online the hassle of returning it makes the chance of it not working too problematic

Run a memory test program to test the stability of the memory also once installed to limit future problems

http://majorgeeks.com/download.php?det=350

and a memory bandwidth test

http://majorgeeks.com/download.php?det=4664

 

So I guess my next question is, how easy/hard is it for me to purchase two more of the "exact" same memory modules once I've bought my initial pair of sticks? Is it just a question of finding it online/offline and buying it, or do the makes get outdated and buried under the masses of other sticks available?

 

It can be quite hard,when a manufacturer releases a dual channel kit not only are they the same make,model ect they are from the same batch and have been tested to work in dual channel

Even small variations in the model of the memory can cause problems,your best bet is to buy the closest possible match to your current memory, even though what your buying looks the same it could have been manufactured on the other side of the planet with different specifications,you will only know when the memory is in your hand and you remove the heatspreaders and compare the two sticks,very few retailers will state what you are getting beyond basic compatibility information and you cannot request for example a BO stepping Intel CPU you just get what your given

Luck really does play a part in this aspect of component purchase hence it being nice if the store you use have a no quibbles return policy

 

For dual channel operation:

• DIMMs must be installed in pairs
• Both DIMMs must use the same density memory chips
• Both DIMMs must use the same DRAM bus width
• Both DIMMs must be either single-sided or dual-sided.

"Everything identical" when adding a second pair of sticks is not necessarily true, even if you're speaking of module size. Most motherboards that support dual channel memory operation will operate as desired with identical sticks in slot one of each bank, and identical sticks of another capacity or even density in the second slots. So you could have a set of 2 512's, and a set of 2 256's-- in the correct slots, of course-- and still have dual channel operation.

 

Also

Both chips must run the same voltage range

Both chips must have compatible memory timings

The only way to be sure all these points are complied with is to buy a dual channel kit or be very specific in your memory selection even if you know what your looking for its almost impossible to find the information you need

I challenge anyone to find two different brands of memory on newegg that match these 6 criteria fro dual channel operation,even the corsair spec sheet doesnt give anything away they even state that they have only tested whether dual channel works on an nforce 2 test setup

http://images10.newegg.com/UploadFi...ligence/Corsair/20-145-491/twinx2048-3200.pdf

these are all the specs you get

SpecificationsModel
Brand CORSAIR
Series XMS
Model TWINX2048-3200
Type 184-Pin DDR SDRAM
Tech Spec
Capacity 2GB (2 x 1GB)
Speed DDR 400 (PC 3200)
Cas Latency 3
Timing 3-3-3-8
Voltage 2.6V
ECC No
Buffered/Registered Unbuffered
Heat Spreader Yes
Warranty
Manufacturer Warranty Lifetime

 

For the sake of argument...let's say your memory slot are two blue ones and two black ones.

The two sticks in the black slots have to be the same and the two sticks in the blue slots have to be the same, but...the memory in the blue slots don't have to match the two in the black slots, as far as size and coding. Obviously you don't want to put in two sticks of ddr 266 and two sticks of ddr400 cause that will make the 400 run at the 266 speed!!

Roger

 

http://forums.majorgeeks.com/showthread.php?t=96703

 

Technically speaking...the ram in one set of dual channels don't have to be identical (as far as brands, chip #'s code #'s etc.)to the other set in order to keep the dual channel feature activated. As stated before...you want to keep the speed, and if possible the "CAS" timing the same, but you don't need 4 exactly identical sticks, it only has to match 2 & 2. However there is always the possibility of the one brand not working with the other, especially if one is name brand and the other generic!! That is possible even under you "normal", single sticks of non-dual channel ram.

So...If I was going to fill two sets of dual channel slots, then if you are going to spring for the cash all at once upfront, and can find two sets identical...then great, go for it...you have the least chance for any conflicts between the two sets, but...if you have four slots, and your wife will only let you buy one set now and you have to wait until your birthday to get the second set, then the odds of you matching, are going to be in the neighborhood of next to nothing!!

Roger

 

Hmmm seems confusing. I guess it's one of those specific scenarios that change per PC and mobo being used. I guess the key is to buy parts from a store from around (local) so that I can return them if need be.

 

It's not that confusing.

Identical is the safest way.

If not, then as long as they are in identical pairs.

Both pairs don't necessarily have to be the same brand.


If you're worried about compatibility, don't buy online as it can be more of a hassle to return and swap things.

 

I have 4 sticks of 512 mb PC3200 ram (samsung brand) in my board running dual channel. Neither pair were "matched pairs" or were a "Dual channel kit." I started with two sticks, then months later purchased the second two - then months after that had a problem with one of the sticks and had to replace it. They all seem to be operating just fine in dual channel mode. The timings are slightly different between the four sticks (haven't tried to change them yet) - but I just made sure the timings that match are paired together. Actually, in point of fact, pairing the timings didn't make a measurable difference - at least not one I could detect.

I also agree that brand is not as important as getting the same type and speed. It's true if you pair 400mhz with a 333mhz stick, all of your ram will run at 333mhz . . . just like a convoy is only as fast as the slowest ship . . .

 

Ok, those last two posts wrap it up much better. That's good to know...at least I don't have to go filling up all my slots right away.

Thanks for the heads up!

 

Good question . . . I'd like to see the answer myself.