Do I need to buy Quad Channel?

h4rm0ny · 30 Nov 2018 at 20:18

Simple question - how important is it that I buy all my sticks of RAM together in a "Quad-Channel" pack rather than say two "Dual-Channel" packs? And can I mix and match manufacturers so long as the speed and timings are the same? If it matters, my interest is in DDR4.

4K8KW10 · 30 Nov 2018 at 21:26

h4rm0ny said:
Simple question - how important is it that I buy all my sticks of RAM together in a "Quad-Channel" pack rather than say two "Dual-Channel" packs?

How memory bandwidth is killing AMD's 32-core Threadripper performance https://www.pcworld.com/article/329...ng-amds-32-core-threadripper-performance.html

h4rm0ny said:
And can I mix and match manufacturers so long as the speed and timings are the same? If it matters, my interest is in DDR4.

No, you need a matched kit from the same manufacturer.

tamzzy · 30 Nov 2018 at 21:47

4K8KW10 said:
No, you need a matched kit from the same manufacturer.

don't spout nonsense.

h4rm0ny said:
how important is it that I buy all my sticks of RAM together in a "Quad-Channel" pack rather than say two "Dual-Channel" packs?

not very

h4rm0ny said:
And can I mix and match manufacturers so long as the speed and timings are the same?

you can mix and match. the ram will automatically default to the slowest of the ram sticks.

if you're going for overclocks, then it's advisable to stick to the same model of ram. if not, then any will be fine.
just note that ryzen is a bit more picky with ram, so mixing and matching may cause some incompatibility if running above rated speeds.
intel is a bit better in this respect

4K8KW10 · 30 Nov 2018 at 21:49

tamzzy said:
don't spout nonsense.

You need matched kit to enable dual channel. I tried on my laptop with 4 identical (what was supposed to be identical) sticks and only 2 of them enabled dual-channel.

tamzzy · 30 Nov 2018 at 21:56

4K8KW10 said:
You need matched kit to enable dual channel.

matched kit is guaranteed to run dual channel, doesn't mean that unmatched kit won't run dual channel.
i've got 3 laptops, all with unmatched ram running fine with dual channel

asynchronous dual channel is less compatible (different ram stick sizes)
for best compatibility: matched pair, then unmatched pair, last of all is unmatched+different size ram

h4rm0ny · 30 Nov 2018 at 22:31

Hmmmm. Conflicting answers. So let me add more detail. I'm considering 3200 DDR4 memory for a Threadripper build. Will definitely be Threadripper. MSI X399 Creation motherboard. I don't intend to do any overclocking although technically 3200 is overclocking. So maybe I do. If for some reason I end up with a bit less than 3200 it's not the end of the world - it's a pro system which will run a lot of VMs. So I want a lot of memory. In shopping for RAM I'm in some cases buying multiple packs of "Dual Channel" RAM rather than specifically advertised as Quad Channel packs. I'd also like to know that I can add more RAM later, hence questions of different manufacturers.

Armageus · 30 Nov 2018 at 22:42

4K8KW10 said:
You need matched kit to enable dual channel. I tried on my laptop with 4 identical (what was supposed to be identical) sticks and only 2 of them enabled dual-channel.

No you don't. All a dual/triple/quad channel kit is, is a 2/3/4 sticks all from the same batch guaranteed to work together.

However buying 2/3/4 individual sticks 99% of the time is fine as long as you match speed and latency. If speed or latency don't match then again most of the time they will run at the lowest supported speed, but some boards/memory can have issues with this.

tamzzy · 30 Nov 2018 at 22:49

ram speeds at XMP/DOCP profiles are set to that particular ram model/matched set
ie a single stick rated at 3200mhz is rated to run 3200mhz by itself, doesn't mean that it will defintely 100% of the time run 3200mhz when paired with other ram. this also applies to pairs of ram - if you buy a matched pair, they're guaranteed to work together at that rated speed - but might not work at that speed when that pair is working with another set of ram.
all ddr4 ram above 2400mhz is (as you say, overclocked) but they'll work at 2400mhz, which is the jedec standard speed. so if you have any incompatibility with non-matching ram - then they all should run when you set it to 2400mhz.

h4rm0ny said:
Conflicting answers. So let me add more detail.

to answer in your case specifically. given that ryzen/threadripper is more ram sensitive, it may make more sense to get a quad channel set.
but yes, as myself, and armageus have said, it's mostly okay, most of the time, to mix-and-match ram.

h4rm0ny · 1 Dec 2018 at 00:30

Thanks all. Well then this frees me up to have a bit more choice in what RAM I get. Sounds like I'm perfectly fine buying 2x the same Dual Channel packs if I want and also alright with getting some more of the same brand and type later on. And probablygetting a different brand if I must, so long as I match the speed, latency and size. I'm not really interested in getting extreme overclocks and can even live with it dropping down slightly if I must, so that gives me a bit more freedom. RAM is so horribly expensive that I want to get the best value for money that I can.

4K8KW10 · 1 Dec 2018 at 06:39

tamzzy said:
matched kit is guaranteed to run dual channel, doesn't mean that unmatched kit won't run dual channel.

There is a probability that it won't run. Actually, in some cases, the RAM modules won't be recognised by the motherboard.
It is about those serial numbers on the sticks - on matched kits I see they are the same, while with unmatched kits you need to be lucky to get, for example, an EZ3-CE6 stick running in enabled dual channel with an MP5-KA3 stick, just as an example.

Armageus · 1 Dec 2018 at 07:47

4K8KW10 said:
Actually, in some cases, the RAM modules won't be recognised by the motherboard.

Never experienced that and you are overstating the probability. Yes there is a small possibility that different modules won't work (or be stable) together, but for the most part it works fine.

I've run systems with 4 mismatched sticks (different brands and speeds) before without issue - it certainly isn't down to what serial numbers you have.

h4rm0ny · 1 Dec 2018 at 11:54

I'm currently going for this:
https://www.overclockers.co.uk/corsair-vengeance-lpx-32gb-4x8gb-ddr4-pc4-25600c16-3200mhz-quad-channel-kit-black-cmk32gx4m4b32-my-49e-cs.html

But do people think it would be worth paying a little more to get 2x these?

https://www.overclockers.co.uk/team-group-dark-pro-8pack-edition-16gb-2x8gb-ddr4-pc4-25600c14-3200mhz-dual-channel-kit-black-my-08l-tg.html

I definitely want Quad Channel because I've seen this has a significant benefit on Threadripper but from your answers seems 2x these will still work. It would drop the latency from 16-18-18-36 to 14-14-14-3.

I also looked at 2x

https://www.overclockers.co.uk/team...3600mhz-dual-channel-kit-black-my-08q-tg.html

which would be faster still but my motherboard is only specced up to 3200 (which is already technically OC'd) so I think the second one would be a waste.

My build will be a 1920x for the time being, with a plan to upgrade to a 2nd or 3rd gen TR when I have more budget next year and prices have fallen a little. Use case is software development (compiling) and VMs.

tamzzy · 1 Dec 2018 at 13:38

if money is no object, then i'd go with the 8pack samsung b-die ram. 3200c14 is sufficient.
failing that, then https://www.overclockers.co.uk/king...d-channel-kit-hx432c16pb3k4-32-my-26m-ks.html
it's £100 cheaper, it's up to you to decide whether that performance difference is worth that £100

h4rm0ny · 1 Dec 2018 at 13:49

tamzzy said:
if money is no object, then i'd go with the 8pack samsung b-die ram. 3200c14 is sufficient.
failing that, then https://www.overclockers.co.uk/king...d-channel-kit-hx432c16pb3k4-32-my-26m-ks.html
it's £100 cheaper, it's up to you to decide whether that performance difference is worth that £100

Well, I wouldn't say money is no object. Otherwise I'd be going for a 2nd Gen TR.

But I could potentially go up by a £100 if it made a noticeable difference. One thing I have in mind is an eye on adding more later on. If buy lesser RAM then I'm stuck at that level. I know how much £100 is worth. I'm not really sure how much 14-14-14-36 is worth, is the problem.

Great catch on the Kingston RAM! If I get the Corsair RAM then I'll get that instead. Or well, you know what I mean.

tamzzy · 1 Dec 2018 at 14:01

h4rm0ny said:
now how much £100 is worth. I'm not really sure how much 14-14-14-36 is worth, is the problem.

going from 3200c16 to 3200c14 may yield 1-2% performance benefit with ryzen/threadripper...possibly only slightly more if the program is heavily ram dependent.
if i recall correctly, ryzen/threadripper plays happier with samsung b-die compared to other ram types - but i think it's only when going for monster overclocks that this matters. most ram should work out of the box fine.

h4rm0ny · 1 Dec 2018 at 14:15

tamzzy said:
going from 3200c16 to 3200c14 may yield 1-2% performance benefit with ryzen/threadripper...possibly only slightly more if the program is heavily ram dependent.
if i recall correctly, ryzen/threadripper plays happier with samsung b-die compared to other ram types - but i think it's only when going for monster overclocks that this matters. most ram should work out of the box fine.

Thanks. My work can be heavily RAM dependent at times, but still a few % isn't much. I'll probably want to go up to 64GB at some point so I think I'll stick with the Kingston and save my pennies.

Thanks for all the advice!