 Wait a second. Everyone knows it's bad to mix and match your memory, but how bad is it? I mean if you found a really sweet deal to double up the RAM in your gaming rig, would you be such an evil person if you pulled the trigger? What if the RAM that's in your system isn't available anymore? Are you stuck with it? FOREVERRRRRRRRRR! Let's find out. After we find out just how smoothly Linus here is going to segue to his sponsor. With GlassWire you can instantly see your current and past network activity, detect malware, and block badly behaving apps on your PC or Android device. Use offer code Linus to get 25% off glass wire at the link down below. We never want to feed you misinformation or myths, particularly if it causes you to miss out on a free or cheap upgrade. So we took five different memory sets from our inventory rated for various speeds and latencies, threw them on an AMD test bench with a Ryzen 5 3600X and 2060 Super and went to town checking configuration after configuration after configuration after. Well, you get the point. And after many grueling hours of mind numbing benchmarks, we're here to give you the exciting results. Guess what? It barely matters, or at least it sometimes barely matters. We created a baseline for reference using two eight gig modules clocked at 3,200 megahertz with primary timings of 16, 18, 18, 36. We ran our benchmarks, took notes, and then started swapping out modules one by one. And you might be as surprised as we were to find out that honestly, for the most part, with two sticks, you can get away with quite a lot as long as you're willing to tweak some values here and there in the system BIOS. If you don't overclock your memory subsystem, and I'm talking either with XMP or manually, RAM compatibility with DDR4 has come a long way to the point where basically it just freaking works. Faster modules will generally have no issues clocking down and running steady with the slower ones, especially if they're under four gigahertz. And our performance measurements demonstrate this with pretty much all of our configurations within the run-to-run variants of our tests. But the enthusiasts among you will know that if you wanna get the most out of a modern system, increasing your memory speed is really important. What if we take then half of our reference kit and half of a slower kit and run them in dual channel at the reference kits frequency of 3,200 megahertz? Our slow kit here is timed pretty similarly, 16, 18, 18, 35. But the traditional rule of thumb is that for every speed bin bump, you would expect to also raise your cast latency by one. I'm really not sure if this is gonna work. Crazily enough though, the results look pretty good. Almost as good as our RAM-styled tech scarf on lttstore.com. And the benchmarks look identical. So what we've managed to show here is that if you get lucky and your mismatched RAM will run at your target speed, there's unlikely to be any performance difference. But remember how I promised we'd find some differences? What happens if we up the ante and mix our 2666 with our high-speed 4,000 megahertz kit? Well, the reason DDR4 4,000 costs more than this stuff is that it's been sorted or binned by the manufacturer according to their internal performance targets. Now, sometimes you get lucky and this puppy will overclock to the moon. But other times you get our little friend, Mr. 2666 here. He managed to be compatible with the big bad extreme gaming modules, but not at their rated speed where the system failed to even power on properly. Things broke down even further when we tried to populate more than two dimslobs. The thing is, the more modules you install, the greater the load on your CPU's integrated memory controller. This didn't cause any performance issues per se, as long as we could get the RAM all running, but it did cause some flaky and undesirable behavior. For example, when we populated three slots with a mixture of our reference and slow modules, the system would post and bench at 3,200 speeds just fine at the start. But here's the thing, AMD's Ryzen processors have a feature called flex mode that allows two modules to run in dual channel with a third running in single channel. That's great for getting maximum performance out of a non-ideal configuration, but you've got to be very careful how you populate your slots. As soon as we put our 2666 module in the B1 slot, it got real unhappy, spitting out memory error codes and getting stuck in a restart loop until we reset the CMOS and dialed it all back to 2666. As for populating all four DIMM slots and getting the system to work, that was no easy feat with only a single configuration posting and only when we toned it all down to meet at 3,200 megahertz. That was below our highest rated module's 3,400 megahertz speed. Funnily enough though, we tried coming back to this configuration later, and despite using the same BIOS settings with the same sticks in the same slots, it actually failed to post properly during round two, which goes to show that while your friend might have no trouble running a poop mix of memory with no performance penalty, you can't count on the same result. And here's the big problem with that. Two mixed modules was pretty much fine, but most people aren't mixing memory at the time that they buy their brand new system. It's when they're upgrading down the line and trying to max out an older system that these kinds of questions come up. So the chance that mixing and matching will result in unpredictability when you're maxing out your system and filling all the slots is just too high to ignore. Speaking of unpredictable, get subscribed so you don't miss the next installment in our crazy Intel Home Upgrade series. Andy's doing a man cave. Back to mixing memory though. Is there anything that you can do to improve your odds? Well, yeah, actually. For starters, buying an upgrade that is rated for the same speed and primary timings will help your chances. And so will finding a module that was built using dies from the same manufacturer. And when I say manufacturer, I'm not talking G-Skill or Corsair or Kingston. I'm talking about the actual chips that are soldered to the module. So if you've got a module here with Samsung B dies, good for you by the way, those are nice, try to get more of the same, even if they have a different logo on the heat spreader. But Linus, you might ask, what about different capacities? Can I pair up similarly spec'd eight gig and 16 gig modules and finally join team dual channel? Yes, you can. It's called asynchronous dual channel. So we also ran benchmarks with different capacity modules of similar speeds. And not only did it all register properly, but as long as your workload doesn't exceed the capacity of the smallest module, you shouldn't notice any performance impact. With that said, we still cannot in good conscience recommend going out, buying whatever set of modules is on sale, rubbing them together for good luck and throwing them at your rig. Both the best and the worst thing about PC gaming is that every system is wildly different from the next to the point where what works for your friend or for us today might not work for you. You might hit the Silicon lottery and get something that overclocks just fine and has perfect compatibility, or you might get something that runs at exactly its rated speed and not a Hertz more. Worse yet, you might land yourself in a restart loop or even run into unpredictable blue screens on a rig that otherwise seems to be working fine. So we would strongly recommend if you're upgrading your memory, flip your current modules on Facebook marketplace or eBay or something and buy matching replacements. If however, you've got the spare parts lying around and you wanna see if you can give yourself an easy upgrade with minimal or no performance loss, and you're not afraid of a little bit of fine tuning in the event of some crashing, the good news is that it can work. So please do some of your own testing and let us know in the comments below just how far you were able to push your mismatched hardware. Who knows, maybe you've had access to a free upgrade this whole time. Just like I upgraded my segue to this one from our sponsor, Micro Center. Get the best prices and best selection on PC hardware and anything else tech at one of Micro Center's 25 locations across the United States. Check out Micro Center's DIY arcade cabinet kits. Each kit includes the arcade cabinet, a 27 inch monitor, two joysticks, 20 arcade buttons with switches, a Raspberry Pi, Atari themed graphics and all the components needed to connect and power the system. The included Atari games SD card comes with over 140 licensed Atari games from their systems, the Atari 2600, Atari 5600 and Atari 7800. I mean, even back then they had console generational names figured out, they add 2600 to every one. Why can't Microsoft do this? Anyway, the point is, if you wanna get more creative, you can choose your own components with the Micro Center retro arcade builder. So click the link below and build your perfect arcade cabinet today. If you guys enjoy these kinds of deep dives into memory, check out our previous look at the performance impact of ECC memory. It is slower, but it might help you keep memory errors at bay. You can check out our findings on that sweet stuff at the link down below. I think we've probably got a thing here.