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Can I mix memory quantities between my two ddr2 channels?

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April 20, 2007 5:00:56 PM

On my Biostar Tforce 550 motherboard, I currently have a 1 gb (2 x 512mb) DDR2 PC2-6400 TWIN2X1024-6400C4 Corsair ram. That leaves the other channel with 2 slots open.. I was planning on populating them with TWIN2X2048-6400C4 which is the exact same type of ram, except its a larger module, holding 2 gb (2 x 1 gb). Together, I figured this would give me a total of 3 gb ram.

Unfortunately, Corsair is telling me I cant mix the sizes between one channel and the other! .. That is, even if the same chips are used and the memory type is identical, the fact that one channel has a 1gb module populated by 2 x 512mb sticks, and the other channel has a 2gb module populated by 2 x 1gb sticks, the SPD will not be the identical because the module size will be different.. Other than that, the sticks are the same, both containing Corsair PC2-6400C4 ram. I had no idea the quantity of memory in each of the two channels had to be the same.. I knew that both slots within Each channel had to contain the same quantity, but I thought the two channels themselves were somewhat autonomous.

This means that, if I want to leverage my current 1gb of ram, I can only buy 1 more gb of the same ram, giving me a total of 2gb. IF I want more than a total of 2gb ram, I basically need to throw out my current 1gb (2 x 512mb) module, and buy two new 2 x 2gb modules (4 x 1gb sticks).

This is what im being told from Corsair:

"Dear Valued Customer,

Adding 2 x 1 GB modules to your existing 2 x 512MB will most likely not be stable and is not recommended. The ICs used for the 512MB modules are different from the ones that are used in the 1GB modules. In order for the system to be stable all the RAM needs to be in sync, and all the ICs on the RAM need to be exactly the same. Since the ICs are not exactly the same on these 2 different sets of modules, there may be instances where the RAM gets out of sync (even if it is in milliseconds) and this can cause errors and crash your system. It is NOT recommended to mix and match any modules together on this platform as it can cause many problems. My suggestion would be to add only what you currently have in your system to the exact part number or replace all the modules with new ones. Sorry about that."

Do you all agree with this?




a b } Memory
April 20, 2007 5:18:30 PM

Did you ask the person at Corsiar what his job title is? He may be a new guy quoting you some idea He has thought up with no real data to back it up. Ask him where he got the information from and if that is Corsair's official policy or if it is his idea. I use 2 x 1 GB plus 2 x 512 all the time without incident.
April 20, 2007 6:07:14 PM

The guy who gave me the information is a Corsair tech rep called 'ramguy' reachable on the net as:

Ram Guy [ramguy@corsairmemory.com]

Sounds like an official corsair rep to me... Its very surprising isnt it, how you have to use the same size modules in each channel???

I bet alot of people here arent aware of that, and its not even posted in the sticky at the beginning of the memory forum.. Sure, each channels' ram slot must match the other slot IN THAT CHANNEL, but having to run the same Size module in each channel? Sure I can see having to run the same basic ram in each ddr2 channel, same timings, same speed, etc.. But same ram Quantity in each channel?

Ive never even heard that Hinted at before!!!!!!!!!
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April 20, 2007 7:51:58 PM

First, Corsair's advice, while well-meaning, is clearly wrong, since they periodically change the components of their RAM modules w/o changing the part number.
However, the OP is slightly confused regarding "channels". His current setup (2x 512MB in dual channel mode) has one slot full and one slot empty *in each channel*. If both DIMMs were in the same channel and the other channel was empty, he wouldn't be able to run in dual channel mode.
So, no problem, just install the 2 new 1GB DIMMs in your two empty slots, one in each channel, and you'll be fine.
April 20, 2007 9:53:52 PM

Quote:
First, Corsair's advice, while well-meaning, is clearly wrong, since they periodically change the components of their RAM modules w/o changing the part number.
However, the OP is slightly confused regarding "channels". His current setup (2x 512MB in dual channel mode) has one slot full and one slot empty *in each channel*. If both DIMMs were in the same channel and the other channel was empty, he wouldn't be able to run in dual channel mode.
So, no problem, just install the 2 new 1GB DIMMs in your two empty slots, one in each channel, and you'll be fine.


How am I confused? Reread the original post again. I never said each channel has one slot populated and one not..

This is what I said: " I currently have a 1 gb (2 x 512mb) DDR2 PC2-6400 TWIN2X1024-6400C4 Corsair ram. That leaves the other channel with 2 slots open"

see? one channel fully populated, the other fully empty.

>> If both DIMMs were in the same channel and the other channel was empty, he wouldn't be able to run in dual channel mode.<<

Now I AM confused!! The 1gb module I have consists of 2 x 512 mb sticks... They each populate the first channel, ie, the two slots of the same color adjacent to each other.. That leaves the other channel, ie, the two slots of the other color empty. This statement of yours is really puzzling. To use dual channel mode, posts slots of at least One channel must be populated. If you populate the slots such that one slot of each channel is populated, and the other slot of each channel is empty, your ram will NOT be reported as functioning in two channel mode!!

The truth that you are incorrect is found by looking at my CPU-Z screen shots in my opening post.. Youll note it indicates Im in Dual channel mode.. And, I have populated the slots as I indicated, ie, fully populate one channel!!!

I just reread the biostar manual, and maybe this is whats confusing you. The ram slots are labeled as follows from one side to the other:
DDR2A1, DDR2B1, DDR2A2, DDR2B2

It looks like you are assuming that a complete channel comprised A1, A2 slots, and B1, B2 slots, but thats incorrect.. A complete channel, and the way they are colored, shows that Channel 1 comprises DDR2A1 and DDR2B1. And, to invoke Dual Channel mode, the instructions say you must populate the A1,B1 or A2, B2 together. Which is just what I did, and its what Cpu-z says has succeeded in invoking dual channel mode.. Aside from that, I appreciate the advice that I should have no problem using different quantity of ram in my other channel than Im now using. I am pissed at corsair , though, for advising me incorrectly.

>>I use 2 x 1 GB plus 2 x 512 all the time without incident.<<

Badge, other than the size difference, are the speed and the timings of your 2gb and 1gb modules the same?
April 20, 2007 10:14:53 PM

Quote:
other than the size difference, are the speed and the timings of your 2gb and 1gb modules the same?


I run 2 x 1GB plus 2 x 512 at 4-4-4-12 @ 1000 mhz in Dual Channel at 2.25 volts.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Wow, Badge, your 1gb module is identical to my 1gb module in terms of speed and timings, only yours is about 30 bucks less than mine was!!! I wonder if the 2gb from Skill could be combined with my Corsair 1gb module since the timings and speed are identical. Do you think you could have run a module with different timings or speed in your 2gb module from your 1gb module, or do you think that would be pushing your luck?
a b } Memory
April 20, 2007 10:23:55 PM

I wouldn't combine different mfg's. if I could avoid it. It may or may not work. I built a system for a friend of my son's recently and combined 2 x 1Gb OCZ with 2 x 512 MB Kingston (both PC3200) and the system ran fine. It would not run at 400 mhz. however. Combining the two mfg's may work, but it may not work as specified. That's all. Things like dual channel may not work as well when combining. However, like Mondoman said 2 x 1GB plus 2 x 512 MB of the same RAM will work fine. That has been my experience.
April 20, 2007 10:45:22 PM

to answer your question YES you can have 2x512 and 2x1GB modules like I do and still run in dual channel, does that help. I have 1x512 and 1GB in channel A and 1x512 and 1GB in channel B. So basically I'm running 1.5GB in each channel.
April 20, 2007 11:19:57 PM

Quote:
to answer your question YES you can have 2x512 and 2x1GB modules like I do and still run in dual channel, does that help. I have 1x512 and 1GB in channel A and 1x512 and 1GB in channel B. So basically I'm running 1.5GB in each channel.


Yes.... thank you. It appears that Corsair is simply protecting their Butts by going way more 'conservative' wrt channel matching than they need to, and in the process, guiding people in the wrong direction. Its wrong because its forcing them to buy ram that willl not necessarily best meet their interests.
April 20, 2007 11:27:10 PM

Quote:
...
However, the OP is slightly confused regarding "channels". His current setup (2x 512MB in dual channel mode) has one slot full and one slot empty *in each channel*. If both DIMMs were in the same channel and the other channel was empty, he wouldn't be able to run in dual channel mode....


How am I confused? Reread the original post again. I never said each channel has one slot populated and one not..
Yes, that's what you're confused about. By definition, if you are running in dual-channel mode, you have some memory in *each* channel. If all the memory is in one channel, by definition you can only run in *single* channel mode.

Quote:

... The 1gb module I have consists of 2 x 512 mb sticks... They each populate the first channel, ie, the two slots of the same color adjacent to each other.. That leaves the other channel, ie, the two slots of the other color empty. ...

This seems to be the root of your confusion. Different MB models use different color schemes on the DIMM slots. Some MBs assign a color to each channel, so to run in dual channel mode (one DIMM per channel), you put one DIMM in one slot, and the other in a slot of the other color.
Other MBs assign one color to the first slot for each channel, and a second color to the second slot for each channel. In these MBs, you put both DIMMs in slots of the same color to run in dual-channel mode.
You seem to have this latter type of MB; on your MB, the two slots of the same color adjacent to each other are one slot from each channel.
MB manuals are frequently very confusing on this subject or just plain backwards. On your MB, the channels are channel A and channel B, each with slots 1 and 2.

hth
April 20, 2007 11:55:44 PM

Ok... yes. good explanation.
April 21, 2007 12:27:24 AM

gigabyte ds3:
I run 2x512 corsair and 2x1024 patriot at pc2-6400 speed 1.8v 5-5-5-12

bench and game the heck out of it, no problems at all
April 21, 2007 12:40:52 AM

Quote:
gigabyte ds3:
I run 2x512 corsair and 2x1024 patriot at pc2-6400 speed 1.8v 5-5-5-12

bench and game the heck out of it, no problems at all


Wimcle... do your 1gb and your 2gb modules have the same ddr2 speed and the same timings, voltage, etc? Are they two different mfgs, but are the ram specs identical? or are they different too? And, if they are different, have you found out what speed or timings concessions are being made to the slower module? No effect on their dual channel capabilities I presume?
Anonymous
a b } Memory
May 5, 2011 9:07:52 AM

Quote:
In order for the system to be stable all the RAM needs to be in sync, and all the ICs on the RAM need to be exactly the same. Since the ICs are not exactly the same on these 2 different sets of modules, there may be instances where the RAM gets out of sync (even if it is in milliseconds) and this can cause errors and crash your system.


What a load of rubbish he is saying, obviously not got a clue about computers or RAM or electronics.

How can the RAM possibly go out of sync when the motherboard is generating a single clock which it supplies the same clock to all modules! It is impossible that there are "sync" issues as the RAM does NOT supply its own clock signals!
!