DDR3 RAM number of slots

Steve Mutchler
Steve Mutchler used Ask the Experts™
Looking at the new Lenovo M90 machines...

Comes with DDR3 RAM...and it appears, from what I can tell that the MB has 4 slots...

We want to configure the M90 with appropriate amount of RAM for when we move to Win 7 - 64, (currently on XP 32)...We belive 6 Gb or RAM would be about right for our use...

1.  With DDR3 RAM...I believe there are 3 "channels"...do we not need 6 RAM slots for this???...potentially putting 2 chips in each "bank of 2 RAM slots"...???
2.  IF the M90 has 4 slots, is one slot a "common" slot to allow all 3 channels...
3.  If we go for 6 Gb RAM...is our best solution to have 3 - 2Gb chips using 3 of the 4 RAM slots???...if so, how do we determine which slot to NOT use...???
4.  Do all RAM chips need to be the same size in DDR3...???...eg: I can't use 2-2Gb chips and 1- 1Gb chip...correct...???

Thanx for your comments
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You say these are M90...what Type ???

But to answer as much as possible without knowing the specific system type:

1. DDR3 can be run in dual-channel or triple-channel.  Triple-channel is still not widely adopted so it is unlikely supported by a Lenovo motherboard.

2. If it has 4 slots, you can install 2 or 4 matching pairs for best performance.  Again, we need the system type to be 100% sure.

3.  For 6GB you should have 2x2GB and 2x1GB.

4. They do not have to all be the same capacity, but each pair should match.
According to the user's guide for the most common M90 machine types:

Your computer has four slots for installing or replacing DDR3 DIMMs that provide
up to a maximum of 16 GB system memory. When installing or replacing a
memory module, use the following guidelines:
v Use 1 GB, 2 GB, or 4 GB DDR3 DIMMs in any combination up to a maximum of
16 GB.
v Install memory modules in the sequence of DIMM 1, DIMM 3, DIMM 2, and

Gary CaseRetired
Most Valuable Expert 2013
Top Expert 2009
The M90's do not use a triple-channel capable chipset (like the X58) ... so they only support dual channel operation.

You'll get the best performance if you only install TWO modules -- installing 4 modules will place a much higher load on the address and data bus and can result in unstable memory operation.

For optimal dual-channel operation you need matching amounts of RAM on each channel -- so I'd suggest you buy a pair of 4GB modules and install 8GB.    Alternatively you could install one 4GB module and one 2GB module if you really want to limit them to 6GB ... it will still operate in dual channel mode, but there will be a slight reduction in memory bandwidth, as it won't be the optimal symmetric mode.


mavaks...This is type 3246...
Specs are i5-750  RAM 3 Gb...The RAM is indicated in our quote from our supplier, Microage...but 3Gb did not seem correct for a DDR3 system...which raised a flag for me, thusly my question here...Supposedly this is one of Lenovo's "Top Seller"...meaning they are keeping it in stock...

So, 3Gb means one 2 gig and one 1 gig stick...which struck me as wrong...

You guys explained a lot...many thanx...

We will have to order these with either 4 Gb or 8Gb or RAM...and 8 is the only option that makes sense runningn Win 7-64...

Thanx for your help...

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