Is It OK To Mix Different Types Of RAM?

Is It OK To Mix Different Types Of RAM?
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Memory standards keep changing and the folks that make it want you to keep upgrading or buying PCs with more memory. For most people running a current operating systems like Windows 10 or macOS sticking with 8GB RAM is adequate.

The computer I’m working from at the moment has just 4GB and it works just fine running Windows 10 with a basic image editor, my preferred text editing app and a few browser windows open. But if you need more – like 16GB or beyond, what are the rules for DIY upgrades?

Assuming your computer can take a RAM upgrade – if you’re the owner of a recent Mac you’re probably stuck with what you bought as Apple solders everything in – then there are a few things to watch out for.

The simplest rule

If you want to minimise the risk of any later hassles, stick to memory of the same brand and spec as what you already have.

If your computer has DDR3 1333 then sticking to the same will minimise the risk of any later system instability. If you get a good deal on slightly faster DDR3 1600 you’ll probably be OK as your motherboard will underclock the faster chips to match the slower one.

Mixing brands is also possible but there are cases where different manufacturers interpret specifications differently. As a result, there can be situations where certain conditions can lead to system instability. And those sorts of crashes can be notoriously difficult to diagnose.

So, to keep things simple and reduce the risk of an unstable system, stick to one brand of memory and one specification.

Mixing RAM capacities

What if your PC has 8GB, comprised of a pair of 4GB chips? If you have a pair of spare memory slots, can you add two more 8GB chips to get to 24GB?

Generally, this should be OK, subject to sticking to one brand and spec. If sticking to one brand isn’t possible – I’d suggest pulling the memory that’s already there and adding new memory from scratch.

For example, rather than keep the pair of 4GB sticks, I’d replace them with a pair of 8GB and get my system up to 16GB or 32GB that way.

It’s worth noting, before you upgrade that different Windows 10 versions can use different amounts of memory.

The 32-bit version of Windows 10 can only use 4GB of memory.

With the various 64-bit versions

  • Windows 10 Home – 128 GB
  • Windows 10 Pro – 2TB
  • Windows 10 Pro for Workstations – 6TB
  • Windows 10 Enterprise – 6TB
  • Windows 10 Education – 2TB

Can you mix different types of RAM?

The short answer is yes. But the path to greatest stability and performance comes from using memory of the same specification from a single manufacturer.

This article has been updated since its original publication.


  • So, to keep things simple and reduce the risk of an unstable system, stick to one brand of memory and one specification.

    This is the best advise. Unfortunately RAM has a multitude of much finer grained timing that just the obvious “1333MHz”. Using something like Mem Tweakit you’ll see there are 6 primary timings dealing with latencies and delays. Then another 9 secondary timings and literally a couple dozen tertiary timings.

    You’d think two sticks that say 1333 should be the same but when they have different CAS or RAS timings… ugh random crashes ahoy! I’d suggest, even when using the same brand that you check the sub timings (especially the primary ones relating to latency) to make sure the timings are the same.

    As for using different sizes, again that can be problematic for exactly the same reason. You’ll often find the smaller sizes will have faster timings than the larger sticks. So if you mix and match you’ll run into the same timing problems and potential crashes.

    And even if you can get all the sticks of different sizes/brands to work together you’ll ultimately wind up having to run them at the lowest common denominator. So you’ll be gimping performance. Often the best solution is to simply buy a complete set of new RAM in the size you want and sell the old RAM on ebay or Gumtree.

    Oh, and that’s before you get to the issue of motherboard support. Depending on the age of your motherboard you may be restricted to the type and size of memory you can install. It may take DDR1333 RAM but be hard limited to 16GB or 32 or 64 or some other seemingly arbitrary number. So make sure you check with the mobo specs to make sure that 32GB of RAM you buy can actually be utilised.

  • Not related to types of RAM but amount:
    I have 8GB of RAM in this desktop that I’m using to type this. My laptop has 4GB and the difference with Chrome is massive. So much faster.

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