Can you mix different memory in installation

I don't recall ever reading anything on this subject but can you mix memory with Windows 11? What I mean is can you install two sticks of 32G DDR4 3200 in slots 1 and 3 of your motherboard and then install 2 sticks of 16G DDR4 3200 in slots 2 and 4?

This might be a motherboard issue but could Windows handle it?

RAM type, speed, size and slot assignment depends strictly on the motherboard and its specs. Windows Home supports 128 GB ram. Pro supports 2 TB ram.

Thanks. Thought came out of a brain fog induced by a weekend of Elden Ring.

Short answer is yes, usually.

You also need to check for latency values, CL
If not same you might experience issues.

I have three laptops with mixed memory modules. Newest one came with an 8GB and a 32GB setup. Never a problem with any of them.

One other quick question before I really screw up the motherboard: in BIOS I can select Profile 1 for the memory (both sticks are DDR4 3200) so the BIOS profile gives me the timing for the currently installed memory. However, the timings on the two other sticks (not installed yet) are different from the current profile. In the BIOS, I have the options to change parameters on each channel. Since the current memory is in channel one, can I change the timings on channel two to match the new sticks timing or would that really screw up the BIOS? I was wondering how the BIOS and Windows would handle two memory channels with different timings on each.

Maybe a dumb question. Sorry.

Specs (manufacturer and model #) of the RAM and motherboard (assuming it is not the one listed in your computer) would help tremendously. For one, we're not sure what Profile 1 means, because that will vary by manufacturer. Additionally, it will really depend upon the RAM specs.

However, motherboard manufacturers might keep a list of 'certified' RAM that will work.

Additionally, the BIOS can try to force settings like timings and such, but if the RAM cannot make use of them it probably will not boot (or else will boot but be super unstable). As long as you're not trying to overclock it heavily, like increasing the voltage by a full volt, it won't actually damage the components, but understanding what the specs are, and more importantly, what your RAM sets can actually do, requires a good bit of research, and is not something that we can easily answer here, at least not without the specs.

Short answer - if they are relatively similar, they should work. Longer answer, typically, motherboard will settle upon using the lowest common denominator, or, IOW, the set of specs that both can relatively easily use. If the newer sticks have tighter timings, for example, the motherboard may force all sticks to use the looser timings of the older sticks, since all sets can use them.

However, with that 'profile' assignment for the motherboard, and the fact that it can be arbitrarily applied to individual banks, that throws things into a whole new arena. Because it sounds like you can assign individual profiles to individual banks, something I've not seen on my motherboards.

So, what RAM sets are you using? And is the motherboard the same as the one you have listed in your computer specs above?

Finally, serious question - why are you expanding past the 64 GB you already have? (Yes, I know, I have 128 GB, but I have very specific reasons for my build, and I'm curious why you're expanding).

Expanding upon this a bit, here is the CPU-Z info for my RAM.



You can see that I am running at XMP specs, which are much higher than the JEDEC baseline specs for the RAM, as this 128 GB set (4x 32 GB modules) was advertised to support that XMP profile, and, indeed, my motherboard is simply running it at the XMP profile built in to the RAM itself.

Current motherboard info:



Current memory spec:



Current memory SPD:



Think about adding:

Corsair Vengence Pro RGB (2x16G DDR4 3200) SPD 16 18 18 36 75 running XMP 2.0

To be fair, you're better off with the same set as you've got, but I understand that is both expensive and might be overkill for you. Those XMP 2 specs are not too far off from the ones you have, it really shouldn't make a difference here at all.

Worst case scenario, you can load the new RAM into the new banks, apply XMP across all 4 banks and see what CPU-Z shows in terms of what the system is making use of., I suspect all 4 will try to run at the specs of your current set, to keep it simple.

If your motherboard allows running different XMP specs simultaneously, then they will probably run their respective specs without an issue.

Worst case scenario, both sets fall back to the JEDEC (non XMP) specs and run a bit slower to maintain stability, though I highly doubt this will happen.

Still curious why you want / need to expand past 64 GB. If you're doing it just to have more RAM, sure, this should work. If you're doing it because you have a need for it, like mission critical stuff for work, running multiple VMs simultaneously for work / testing / learning, I really think you should explore getting the same 64 GB set you've already got, and running all banks as a fully matched set. They will still not be completely matched, as they are from 2 separately purchased sets (and thus probably from different batches, with different mem modules on the sticks between sets), but overall, less chance of instability.

If this is for fun, or at least not for anything mission critical, what you want to do right now should be perfectly fine.

Another scenario: I do not specify XMP and enter the SPD for each channel manually. Ch 1 would run the SPD for the current sticks and ch 2 the SPD for the additional sticks. Thought is that if the BIOS was only meant to run both channels as one SPD, they wouldn't have added the second channel option for configuration (ch 1 at 16, 20, 20, 38, 75 and ch 2 at 16, 18, 18 36, 75).

This issue is definitely related to hardware compatibility, particularly the motherboard and BIOS/UEFI, rather than the Windows operating system. In theory, yes, you can mix different sizes of memory as long as they are the same type (in this case, DDR4) and the motherboard supports the memory size and speed. However, it's always best to refer to your motherboard manual for specifics on memory configurations. Some motherboards may have very specific rules about what types of memory configurations they can support.

As for Windows 11, it is generally agnostic about the specifics of your RAM. It doesn't particularly care about the arrangement or sizes of the sticks. The most important thing is that the total amount of RAM is within what Windows 11 can handle. Both Windows 11 Pro and Home 64-bit versions can support up to 2TB of RAM, which is far beyond what you're proposing here.

However, it's worth noting that mixing RAM sizes can potentially disable the dual-channel functionality, which can impact performance. Dual-channel mode requires two identical memory modules, and it roughly doubles the bandwidth available for the memory, thereby improving overall system performance. When you mix sizes like this, the motherboard will typically drop down to single-channel mode, which can have a performance impact.

Again, you'll need to refer to your motherboard manual for specifics on memory configurations and dual-channel support. In some cases, modern motherboards might be able to run in a mixed dual-channel mode, known as "flex mode", where the matched sticks run in dual-channel and the unmatched part runs in single-channel. However, this is highly dependent on the specific motherboard and BIOS/UEFI implementation.

rzn6jw said:

One other quick question before I really screw up the motherboard: in BIOS I can select Profile 1 for the memory (both sticks are DDR4 3200) so the BIOS profile gives me the timing for the currently installed memory. However, the timings on the two other sticks (not installed yet) are different from the current profile. In the BIOS, I have the options to change parameters on each channel. Since the current memory is in channel one, can I change the timings on channel two to match the new sticks timing or would that really screw up the BIOS? I was wondering how the BIOS and Windows would handle two memory channels with different timings on each.

Maybe a dumb question. Sorry.

Click to expand...

In most cases, your BIOS won't allow you to set different timings for different channels or different RAM sticks. This is because the memory controller, which handles communication between your CPU and your memory, usually operates on a 'one setting fits all' basis. The controller can't handle different timings for different memory modules, as it needs to send the same control signals to all of the memory at the same time.

When you mix memory modules with different timings, the BIOS or UEFI usually sets the memory timings to the slowest (highest) timings of any of the modules to ensure stability. That is, if you have one module that requires a CAS latency of 15 and another that requires a CAS latency of 17, the BIOS would set the CAS latency to 17 for both modules.

For your specific scenario, it would be best to match all the memory modules with the same speed and timings to ensure stability and the best performance. While it is technically possible to mix and match RAM with different speeds and timings, it can lead to a variety of potential issues, such as system instability or even failure to boot.

If you try to manually set different timings in the BIOS for different memory slots or channels, the best-case scenario is that the system will ignore your settings and default to the slowest compatible timings. In the worst-case scenario, your system might fail to boot, and you would need to reset the BIOS settings to get it to boot again.

Consult your motherboard manual or manufacturer if you're unsure about what your system can handle, as different systems can have very different capabilities and limitations.

I second all that.
An exact match will always provide the best speed and stability.

Just curious, how come this thread is running on 2 places at once concurrently.
DIY Builds and Motherboards AND
Installation, Updates and Activation

Or has my web browser gone crazy?

Thanks for the great insights. Won't take a chance and will leave well enough alone.