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Mixed memory sizes in dual channel slots

HeneryH
Level 7

‎11-11-2019 06:50 AM - last edited on ‎03-05-2024 06:24 PM by Community Admin

I have a question about dual channel memory configuration and adding mixed modules.

I have 8gb x 2 in A2 and B2 now.

I want to add more memory and was wondering if, to allow flexibility in the future, if this was allowed...



I think the manual is telling me that if I use the above config then the first 16 (8+8) in channel A and the first 16 (one of the 16s) would be in dual channel access mode while the remaining 16 would be in single channel mode.

If that is the case, could I take a baby step and just use one 16?



Thanks
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haihane
Level 13

‎11-11-2019 07:00 AM

If that is the case, could I take a baby step and just use one 16?

then you'll lose dual channel memory. this will take a hit on memory performance.



i'm afraid i can't answer the rest of the questions.
meee avoid mixing ram sticks of differing sizes. it should still work if all you're concerned is total ram size detected.

general rule of thumb i heard was, it will run at speeds depending on your lowest stick speed.

so if you have 4 sticks:
- 2 sticks 8 GB, at maybe 2133 MHz, maybe CL 12 ?
- 1 stick 16 GB, godlike 4000 MHz CL 16,

end result: 32 GB at 2133 MHz, CL... uhh... out of my area of knowledge. if i were me, i'd be glad if it boots up and passes all mem86 tests.
aida64 memory benchmark might take a beating tho.
no siggy, saw stuff that made me sad.
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HeneryH
Level 7
In response to haihane

‎11-11-2019 08:07 AM

They'll all be the same brand and timing specs, just different sizes.

The MoBo manual says this
You may install varying memory sizes in Channel A, and Channel B. The system maps the total size of the lower-sized channel for the dual-channel configuration. Any excess memory from the higher-sized channel is then mapped for single-channel operation.


but I am not 100% sure of my interpretation of the statement.

Now that I read it again, I think this config should allow all 32 in dual channel mode:

  • Ch A1 = 8
  • Ch A2 = 16
  • Ch B1 = 8
  • Ch B2 = 16



For some reason at first I thought this was preferred but now I doubt it:

  • Ch A1 = 8
  • Ch A2 = 8
  • Ch B1 = 16
  • Ch B2 = 16


To make a half step towards the end goal and save $80 in the short term, do you thinkg this would be OK?
For some reason at first I thought this was preferred but now I doubt it:

  • Ch A1 = 8
  • Ch A2 = 8
  • Ch B1 = 16
  • Ch B2 = vacant
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haihane
Level 13
In response to HeneryH

‎11-11-2019 10:16 AM

umm, A2 B2, 8 gig sticks, perhaps?
to enable dual channel memory (hopefully)

single stick, stick then wherever else is left.
no siggy, saw stuff that made me sad.
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JohnLockeG
Level 7
In response to haihane

‎11-21-2022 02:44 AM

I'm wondering about this:
In my case I'm using 2 DDR RAM kits as follows:
1) Corsair XMS3 DIMM Kit 16GB, DDR3-1333, CL9-9-9-24 (CMX16GX3M2A1333C9)
2) Corsair XMS3 DIMM 4GB, DDR3-1600, CL9-9-9-24 (CMX4GX3M1A1600C9)
I installed them like this:
A1: 1* 8GB CMX16GX3M2A1333C9
A2: 1* 2GB CMX4GX3M1A1600C9
B1: 1* 8GB CMX16GX3M2A1333C9
B2: 1* 2GB CMX4GX3M1A1600C9

While POST he shows me only 12 GB of RAM.
But in BIOS he shows me all the 20 GB of RAM.

What's the problem? How much can the PC use at the moment?

96409
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ahfoo
Level 13

‎11-21-2022 09:34 AM

That the ending address memory of the mother bios detected. It will not reflect the total available ram the system can provide. In short never mixed ram. The performances will not be actually right. that my opinion. Asus and other mobo manufacturer tested ram in pair or quad pair kit except mix ram combo.
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