Memory for Threadripper

h4rm0ny · 4 Nov 2018 at 20:34

I'm building a threadripper system - 1920X, MSI X399 MEG motherboard and 4x8GB Corsair 3200 RAM. I have a view to update the 1920X in the future when prices of the 2nd Gen high-core Threadripper chips have fallen a lot.

I just watched this video. Including it for reference but basically he says that if you fully populate the RAM you can't go over 2600MHz. That wont be a problem right now but like the processor, I plan to add to the RAM later. Probably buying an identical 4x8GB Corsair Quad Memory slot.

https://www.youtube.com/watch?v=UC67mFBuM8Q

Is what he says true? And if so, then I should either return the RAM and 2x16GB sticks (though then I lose out on Quad channel in the meantime). Or else I should return the RAM and get 2600MHz sticks (don't want to do this - I want fast memory).

Please advise me!

Minstadave · 4 Nov 2018 at 20:40

32GB of RAM is a fair chunk, are you likely to need more?

Having 8 sticks in the system will put more stress on the memory controller.

I'd stick with 32GB of faster RAM for now and if I did need more RAM sell it and buy 4x16GB down the road.

h4rm0ny · 4 Nov 2018 at 20:53

Well I actually might. I work with databases and multiple VMs. I can manage with 32GB (I'm only on 24GB now), but I had hoped to bump it up to 64GB later on.

So it's true, then? Filling all the memory slots will sink my performance?

sandys · 4 Nov 2018 at 21:07

performance will drop off when you add more sticks, that is fairly normal across all platforms but it will all depend on how lucky you are with memory controller and DRAMs.

GSkill do have an 8x16Gb kit running at 2933 which is pretty good going considering load etc, so it's not out of the realms of possibility you could match or do better with a touch of OCing and time.

https://www.gskill.com/en/press/vie...tions-for-amd-ryzen™-threadripper™-processors

Gen1 chips will likely struggle more.

h4rm0ny · 4 Nov 2018 at 22:13

Okay. I'm now thinking I should switch and get 2x16GB. Which prompts two questions:
1/ Do I really need to buy a "Quad-channel" pack of RAM or will I be fine with getting 2 sticks now and 2 sticks at some later date?
2/ In the meantime, am I losing out on performance by only having two sticks rather than four, given it can support Quad Channel memory?

Minstadave · 4 Nov 2018 at 22:24

You don’t need quad channel packs but it may be an issue trying to run two different types of chips. Memory manufacturers change their ICs regularly so even “Corsair 3200mhz” will have multiple different memory ICs through its manufacturing life.

Running dual channel will lose you performance on TR:

https://www.phoronix.com/scan.php?page=article&item=threadripper-linux-ddr4&num=1

sandys · 4 Nov 2018 at 22:24

You will be fine getting sticks now and two later, providing you can secure two equivalent sticks, you will of course only be running Dual channel ram, I'd go with 4x8 now and 4x16 later if needed selling the old lot.

Only you will know if your use case with benefit from the bandwidth, for me the step from Dual to Quad is only measurable in single digit percentages, but I had Dual to start with and always wondered if I would get more performance so bought more, little bit disappointing in my case to be honest, all though this systems feels like the best system I have ever owned, everything is so slick and stable.

h4rm0ny · 4 Nov 2018 at 22:56

Minstadave said:
You don’t need quad channel packs but it may be an issue trying to run two different types of chips. Memory manufacturers change their ICs regularly so even “Corsair 3200mhz” will have multiple different memory ICs through its manufacturing life.

Running dual channel will lose you performance on TR:

https://www.phoronix.com/scan.php?page=article&item=threadripper-linux-ddr4&num=1

sandys said:
You will be fine getting sticks now and two later, providing you can secure two equivalent sticks, you will of course only be running Dual channel ram, I'd go with 4x8 now and 4x16 later if needed selling the old lot.

Only you will know if your use case with benefit from the bandwidth, for me the step from Dual to Quad is only measurable in single digit percentages, but I had Dual to start with and always wondered if I would get more performance so bought more, little bit disappointing in my case to be honest, all though this systems feels like the best system I have ever owned, everything is so slick and stable.

Thanks, both. That's all useful. Well it looks like Quad does have benefits. Hard to say how much difference it will make with VMs and databases, but if compression is typical for high memory applications I could see it mattering to databases. I could just buy more memory now but it's more than I want to spend. So I'll follow the suggestion of sticking with 4x8@3200 for now and plan to sell and rebuy later. Who knows - it will be a little while before I upgrade the CPU. By that time, maybe Threadripper 3 will be around and it will have an awesome handle-anything memory controller and it will be less of an issue. (Maybe).

Thanks. This has really helped.