Can I mix 16 GB and 32 GB RAM? (DDR5)

[Morgh]

I know this wouldn't be an option with DDR4 as I would need to get a 2nd 16 GB, but with my currently factory installed 16 GB DDR5 it is already running in dual channel - so if I get another 32 GB, it should also be able to run dual channel - is it going to be fine?

(I *could* get another 16 GB of the same type that is installed but the max supported is 2x32 and I'll be probably using this machine for at least 5 years so I would get 32 now - working now either at 32 GB with a single stick or 48 if I can mix the new one and the old one and then buy another 32 in a few years...)

[DevaVictrix]

I’m lost with the ddr4/5 thing… really, you want dual channel and the sticks need to be the same size for that. 2x16gb is plenty to last the next 5 years.

[_I_]

yes
but it will not be dual channel mode, but mixed/hybrid/flex mode

2x the smaller dimm in dual ch speeds (2x16 = 32g)
and the remaining of the larger dimm at single channel speeds (32-16 = 16g)

and when mixing dimms its speeds will be limited to the slower dimm
xmp may not work unless both support a similar profile, speed/timings/voltage
or if you look at their profiles you can pick the best common speed, timings and voltage that both kits support


if its a laptop, with 16g soldered to the board and only a single so-dimm slot, get a 32g dimm, its speeds will be limited to the onboard ram, and its smart enough to only use the slower half part of the ram after the faster part is in use, never using its single ch for igpu

[Morgh]

Even my single DDR5 runs at dual channel as this is an inherent property of DDR5

I have only 2 slots. I guess I'll get an identical die to what is currently installed and run with 2 x 16 GB for the time being hoping that it will be enough (with just 16 GB I'm often running at 95%+ of total RAM capacity)

[DevaVictrix]

I think you still only get half the bandwidth if you have a single stick of ddr5.

[De Hollandse Ezel]

you can put in 2 sticks of ram of any size and speed yes.

however... it will cause issues.
at the very least all ramsticks will run at the lowest mhz and cl of the two.

so say you have one stick of 6000 mhz cl30 and one stick of 4200 mhz cl21
-
than they both will run at 4200mhz cl30

so the WORST combination of the both.
and thats in a GOOD scenario..

for mixing them.. might cause instability issues.. in which case the ram will default to the system stock speed.. (which is 3600mhz on newer ddr5 boards.. but 1833-3200mhz on ddr4 boards (with the number varying how recent your chipset is)

mixing sizes logically will give a higher chance of triggering this instability...

heck this instability may even trigger if you combine 2 sticks of same size, same speed and sale cl and same product code.. but of different batches (it is why kits excist.. kits have been tested to work stable together.. buying 2 identical loose sticks.. will not always stable boot (chance is higher they do if bought together and of the same batch but still not guaranteed)

so CAN you mix ram of 2 different sizes.. and still boot yes.
will it be FASTER than just use 1 of those 2 sticks... ONLY if your actually were bottlenecked by amount of ram
buing a new kit with 2 sticks of the same size and speed is always the better and faster option.

if you need 48gb.. just buy 2x24gb kit.. won't be that much more expensive than one single 32gb stick.