Published on July 28th, 2017 | by GaK_45


The Impact of Mixing RAM Speeds

The Impact of Mixing RAM Speeds

The one question we get asked by novice computer builders the most is in regards to mixing new and old RAM. Usually this crops up when someone goes to upgrade their existing system and then runs in to the age-old question that boils down to: “do I have to replace all my RAM or can I just stick more in there?”. That is actually a good question as it shows that someone is learning about Mr. Murphy and his perverse sense of humor.

Our short answer is always ‘It depends, but probably no you don’t have to throw out your existing RAM and replace it all’… then we proceed to ask a few simple questions so that we can give them a much better answer than some mystic Zen ‘wise old teacher’ teacher line that just annoys the average person looking for a straight answer. It really all boils down to what system they are using now and what they plan on upgrading to; what they want their new and improved system to do (and what they want to do with it); what set of RAM they are looking at to purchase and what they have now.

The long answer to this question is how this article came about. Over the next couple pages we are going to over some most common scenarios and give our recommendations on what we would do if it was ‘our system’. Of course, no single article can cover all scenarios and all possible issues but these are probably the most common. Just understand that these are examples and that with these examples you can make a more informed decision on when it is a good time to carry over old RAM, and when it is a better time to pull the trigger on entirely new RAM sets. So sit back and let’s explore the ins and outs of RAM and when it is, and is not, a good idea to carry over old RAM into a new system.

About the Author


"Knowledgeable, opinionated and not afraid to ask the questions you can’t or won’t." GaK_45's combination of multiple industry certifications(MCSE, CCNA, various CompTIA, etc), and over twenty years' experience in the computer industry allows him to provide detailed analysis that is as trustworthy as it is practical.

  • Shark

    did you also test how it affects performance when you add a single RAM module to an dual kit?

    i ask because i have 2×8 GB ram and now i got a 8 GB modul (same specs and brand) from another system i could use.

    but then it´s not dual channel.

    i am using an intel LGA 1155 board.

    would memory performance go down with this thrid stick?

    • gak_45

      Usually what happens when you add in a third stick is the memory controller reverts back to single channel mode. Thus you gain more capacity but performance goes down. How much it goes down depends on what you do with your system. If it is day to day tasks that are not ram intensive (or specifically ram bandwidth and latency intensive) you ‘may’ not notice the loss. If you are doing things that are time sensitive it may/will be dog slow.

      Basically expect a single digit percentage performance loss in MOST games, even loawer for web-browsers/word/etc… and anywhere from 25-50 percent loss in ram intensive scenarios… as long as ram capacity was not a bottleneck in the previous dual chan config. If it was the difference will be reduced… usually.

      Personally I would recommend getting a fourth stick and not bothering with single chan configs. A single stick of ram is a pretty small investment all things considered. But of course YMMV.

      Hope that helps

      • Shark


        problem is i looked but i can´t buy a single stick of that ram.

        i only saw dual kits during my research..

        • gak_45

          I’m not sure where you are located, nor the timings and speed of what you have now, but Kingston, Crucial, Corsair, GSkill, etc all have single stick options. Stick in a single stick of the same timing and speed and dont worry as much about the name on the DIMM. Optimally it would be the same model as what you have now… so if possible get that, but same voltage/latency/speed is usually good enough as most are using the same ICs on their DIMMS.

          for example (assuming you are in the US):

          Other option is to hit up a local PC repair shop. They should have a bin of DDR3 in the back (or at least will if they are worth their salt). Probably set you back about 50-60 bucks for a single 8gb stick. Maybe more, maybe less. DDR3 is all but EOL these days sooo sooner you do the upgrade the easier it will be to do.


          • Shark

            ok, i found one that seems to have the same specs. but it uses a different headspreader and name (thought also from g.skill).

            guess i go for that then.

            i am from europe by the way.

          • gak_45

            Well then a belated welcome from this side of the pond!

            As long as the voltage, timings, and rated speed is the same it should not pose a problem. Could simply be the same ICs with a different level of QC/market segmentation/etc. Basically the heatspreader is just for marketing purposes as DDR3 and DDR4 simply do not need a heatsink unless you OC the living hell out of them… and even then a fan (ie active cooling) is better.

            If they are different it is VERY rare that different ICs with the same rating will cause a problem. So much so that I have only seen it happen once, or maybe twice, in the past couple decades – and even then it was from a bad IC on one of the old DIMMS that was the root cause.

            Good luck and glad you like our reviews.

          • Shark

            indeed i do.. 🙂

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