Added a 3rd stick of RAM and now only in single channel?

hyawatha15

Distinguished
Nov 13, 2007
5
0
18,510
I originally had 2 gigs (2x 1gig)of Ram and I just recently purchased a 3rd chip which is exactly the same type of memory as the original 2. Before I added the stick, I was in dual channel, but now that I added the 3rd, CPU-z says that I'm only in Single channel.

How can I fix this?

Would Buying a 4th stick of the same memory fix the problem? (any other solution of possible.)
 

dmacfour

Distinguished
Jul 11, 2006
269
0
18,780
dual channel only works with two sticks of memory that are of equal size... adding another of the same size would work, but unless you have windows x64 your computer will only recognize it as 3 gigs.
 

dmacfour

Distinguished
Jul 11, 2006
269
0
18,780
ya just make sure you buy one that matches and you should be good for dual channel. the key is in a set of matching memory sticks... you may have two matching sticks, but the third one cancels the whole thing out.
 


two channels - A and B have to have matching memory on each for it to work in dual channel
 

hyawatha15

Distinguished
Nov 13, 2007
5
0
18,510
Ok, so before I go and buy the 4th stick, I want to make sure I'm understanding this.

Since I have 3 sticks of the same memory, it wont work in dual channel, but if I go ahead and buy the 4th stick of the exact same model number, it WILL then work in dual channel?
 

purplerat

Distinguished
Jul 18, 2006
1,519
0
19,810
Dual channel requires RAM to be in pairs. However with three gigs I doubt adding a 4th will really help very much. Neither the extra memory nor the boost of dual channel will really add much unless you're doing some very memory intensive apps.
 

hyawatha15

Distinguished
Nov 13, 2007
5
0
18,510
well, the thing is, I play some intensive games like Crysis, Battlefield 2142 and 2, and games with the Unreal 3 engine. Plus, I'm starting a game development school in a couple of weeks. I know that 2 gigs was kinda holding me back as I was very close to using that up before I even tried Crysis. So, I think getting the 4th stick will be a smart move.
 

cpburns

Distinguished
Aug 28, 2006
239
0
18,680
i ran dual channel back on a nforce2 ultra 400 using technically unmatched ram. both sticks were ddr333 kingston ram though. the same stuff, bought at different times from different places, is STILL working fine though, about 4 years laters. if you're going for dual-channel, just make sure channel A and channel B are matched, meaning:

slot1(cA1): kingston ddr400 1gb
slot2(cB1): kingston ddr400 1gb
slot3(cA2): corsair ddr400 512mb
slot4(cB2): corsair ddr400 512mb

your motherboard's slots are likely arranged differently, but my point stands. make sure the contents of the slots match up symmetrically. it SHOULD work in dual-channel mode.

again though, dual channel ONLY works with multiples of two sticks. the dual controllers will not split the third stick and each access half of it.

slot1(cA1): kingston ddr400 1gb
slot2(cB1):
slot3(cA2): kingston ddr400 1gb
slot4(cB2):

will only result in 2GB of single-channel memory. if the dual memory controllers (yes, there are actually two inside the dual-channel memory controller) detect they're not looking at identical memory configs, one will let the other do everything and pass through it to access all slots, resulting in single-channel memory.
 

LkS

Distinguished
Dec 6, 2007
71
0
18,630
Motherboards using the Intel P35 chipset (and probably the newer ones too) can run dual channel mode with any RAM combination. Otherwise it has to be even no.s of modules.