(dramatic music) - 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 and 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 forever? Let's find out. After we find out just
how smoothly Linus here is gonna segue to his sponsor. With GlassWire you can
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get 25% off GlassWire at the link down below. (upbeat music) We never wanna 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, throw 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 6-18-18-36. 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 freakin' 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 kit's
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 CAS latency by one. I am really not sure
if this is gonna work. Crazily enough, though, the
results look pretty good. Almost as good as our RAM style
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 you're 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 2,666 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'll over
overclock to the moon, but other times, you get our
little friend, Mr. 2,666 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 DIMM slots. 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 gotta 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 2,666. 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 modules 3,400 megahertz speed. Funnily enough, though, we tried 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 is doing a man-cave.
(clicking tongue) 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 specced "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
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Why can't Microsoft do this? Anyway, the point is, if
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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 findings
on that sweet stuff at the link down below Or I think we've probably got
a thing here. (clicks tongue)
