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I've bought a new laptop - MSI Pulse GL66 with 16 GB RAM (2 * 8GB sticks). I'm looking to upgrade the RAM to a higher configuration, as I have to run multiple VMs on this machine. The laptop supports up to 64 GB of RAM as mentioned on the website. I'm a little short on budget as of now, so I thought to swap out one of the 8GB sticks with 32 GB and use it as of now, with other upgrades coming in later.

Would such an imbalanced configuration have any impact on performance? Should I wait and save up for upgrading to 64 GB directly, or should I do it in two steps? Are there any significant drop in performance in the 'flex' mode?

The concerned RAM I'm looking to buy is linked here

2 Answers 2

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Probably not. As both sticks fill up, at some point, the 8GB stick willl be full, and it will start working on only continueing to fill up the 32GB stick. This means it will temporarly work in singe-channel mode, which decreases the performance by about 30%. Still, this is much faster than having not enough RAM, which means it will write the overflow to the SSD, which is much slower, even than singe channel RAM.

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    RAM doesn't really work like buckets filling up with water. It's randomly accessed so you can't say that only one stick is ever being used. If one stick is full then that's because programs are actively using that stick! Also, single channel is something that is enabled as soon as the system POSTs and figures out what mode to run its RAM in. The RAM is either capable of running in dual channel mode or it isn't, it can't switch dynamically or else you'd be able to just run in dual channel mode in the first place.
    – Romen
    Mar 31, 2022 at 15:38
  • Really? I did not know that...
    – Irsu85
    Apr 1, 2022 at 7:47
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    Well RAM isn't hot-swappable, so why would the single/dual channel mode ever change? ;)
    – Romen
    Apr 1, 2022 at 13:11
  • with one 8gb and one 32gb dimm, one being 25% the size of the other, fact is once 16gb worth or more of ram is in use then that smaller 8gb dimm has to be full if dual-data rate (DDR) is/was functioning. Once one dimm is 100% the dual part of DDR stops, and performance decreases (the original question here ). Which is why, with RAM, for DDR to work properly and always) that you use the same size DIMMs whenever possible. But you are not required to. Same principle applies if you have only 1 DIMM installed when you should have 2 DIMMS to have DDR.
    – ron
    Aug 22, 2022 at 14:29
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    The other big thing is something like one DIMM being PC4-3200 vs PC4-2400. From this perspective you would lose out on performance when one DIMM downclocks to match the other; the slower RAM can't magically upclock to meet the faster ram. But if both DIMMs, while different in size, have the same clock speeds then performance would/should not be lost until twice the size of RAM of the smaller DIMM happens, where you then lose out on performance via DDR.
    – ron
    Aug 22, 2022 at 14:33
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As far as I know, installing a second chip of a different size will not allow the ram to function in dual channel mode. So yes, the performance will be slower than if you had 2 chips the same size. But it will still be faster than reading from the page file (hard drive) if you are constantly maxing out your memory. With only 8 gb, that would happen fairly often depending on what you do.

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