What actually needs High speed RAM?

[eric6]

I'm looking to build a new rig pretty soon and I'm wondering if I should bother with High speed RAM or not. I watched the DDR3 video from 2013 on the subject which made it sound like there are only niche use cases where high speed RAM makes a difference but I do a lot of things which are pretty niche so I'm wondering what some examples are? Running VMs? High SQL usage (like on an SCCM primary site server with onboard database)? I'm also wondering if there are any changes with DDR4 since that's what I'll be getting in the new rig. I'm almost thinking of just getting some high speed RAM just in case it benefits me, I mean it shouldn't perform worse, right? those graphs in the 2013 video made it look like there wasn't much difference but it was actually the same RAM, just clocked differently.

 

Side note: I have most of my other parts picked out but I am also trying to decide between AIOs and custom loop for the water cooling.

[Trevor87]

One question are you going to but a GPU in your system?

[Rohime]

With DDR4 there is even less difference than DDR3.    Rendering is probably main one (common use case) or niche cases like vMotion / Live-Migration with Hypervisors.

[Matias_Chambers]

In CPU intensive tasks and games faster RAM can actually make a difference. Think of it as adding more CPU performance. 

[HKZeroFive]

Ignore that awful video for two reasons.

 

1. Linus uses highly GPU-bound settings with a mediocre card (GTX 660Ti).

2. He doesn't measure the minimum framerate which is arguably the biggest impact from faster RAM.

 

Faster RAM can give a performance uplift in a wide variety of things such as gaming to rendering. And in most cases, a kit of 3000MHz RAM in comparison to a 2133/2400MHz one is only a few bucks more.

 

Also, not to sound overly dramatic, but I've been using Digital Foundry's superb videos to battle the misinformation that Linus (unintentionally or not) has been spreading. Here are a few:

 

 

The bottom line is that faster RAM will primarily give higher minimum framerates. But in situations where you are CPU-bound (or bottlenecked by the CPU), you will see higher average framerates. So if faster RAM doesn't cost that much more, I highly suggest you go for it.

[Morgan MLGman]

What's to remember when buying RAM, that you often have to pay like 10$ for a 3200MHz kit over a 2400MHz kit and the difference in some CPU-heavy games is up to 20 FPS (!!!), soooo... 10$ for such a difference? It's just worth it.

 

Though you also can overclock if you get lucky-enough. My Corsair Vengeance LED White kit (2x8GB) is 2666MHz in XMP, I just set the timings and clock speeds to the exact same values as a 3200MHz kit of the same RAM has and it's 100% rock-solid stable with amazing bandwidth scores.

[porina]

A simply generalisation is the faster the CPU is, the faster the ram should be to keep up with it. There isn't a single "good enough" line to aim for, and it can also vary depending on the structure of the ram itself. For a fast modern Intel quad core, I'd aim for something a bit faster than stock ram since there isn't normally that much of a price difference. Also I'd always add ram in pairs to make use of dual channel mode. To not do so halves your ram bandwidth.

 

In my own uses, prime number finding software can be very demanding on ram bandwidth, not so much on latency. To be practically ram bandwidth unlimited as a rough guide, aim for a ram speed in dual channel mode to be comparable to the CPU clock. I do not meet this myself, as my fastest system runs at 4.2 GHz and ram at 3200. I don't want to deal with the cost and compatibility of even faster ram...

[xentropa]

Encryption and SHA is the only thing I can really think of.

 

Everything else, not so much.

[eric6]

12 hours ago, Trevor87 said:

One question are you going to but a GPU in your system?

I don't see how that's really relevant tot he main question maybe to the side note but "rig" implys gaming which implies high end graphics card and why would I be considering a custom loop without a GPU? I'm considering a water cooled GTX 1080 which come with AIOs or blocks for custom loops.

11 hours ago, porina said:

A simply generalisation is the faster the CPU is, the faster the ram should be to keep up with it. There isn't a single "good enough" line to aim for, and it can also vary depending on the structure of the ram itself. For a fast modern Intel quad core, I'd aim for something a bit faster than stock ram since there isn't normally that much of a price difference. Also I'd always add ram in pairs to make use of dual channel mode. To not do so halves your ram bandwidth.

 

In my own uses, prime number finding software can be very demanding on ram bandwidth, not so much on latency. To be practically ram bandwidth unlimited as a rough guide, aim for a ram speed in dual channel mode to be comparable to the CPU clock. I do not meet this myself, as my fastest system runs at 4.2 GHz and ram at 3200. I don't want to deal with the cost and compatibility of even faster ram...

Well, i'm going 7700k so fastest single threaded performance out there, you make it sound like fast RAM would be worth it in that case but maybe not fastest RAM. The motherboard will probably end up being one of the " ASUS ROG Maximus IX" boards so show they support up to DDR4 4133(O.C.). and G.SKILL sels up to DDR4 4266 (PC4 34100) but both of those drop to 19 CAS latency and DDR4 4000 (PC4 32000) is 18 CAS latency so I might go DDR4 4000 (PC4 32000). I know about the pairs for dual channel thing already but good to mention in case I hadn't or someone else sees that who didn't.

[porina]

8 hours ago, eric6 said:

Well, i'm going 7700k so fastest single threaded performance out there, you make it sound like fast RAM would be worth it in that case but maybe not fastest RAM.

This is one of the cases where single threaded performance doesn't matter. It is only when you use multiple threads can the total memory bandwidth get limiting. So as much as I would love faster ram in my uses where I know it has a benefit, pricing one you get to the 3000's starts to climb rapidly. Unless you know you have something that benefits it, I wouldn't recommended getting the fastest. If you do, you'll never have to worry about it again, but I'm also a bit cautious about compatibility of the fastest speeds. Otherwise, the low 3000's is more reasonably priced and yet still gives a good boost above basic speeds.

[eric6]

2 hours ago, porina said:

This is one of the cases where single threaded performance doesn't matter. It is only when you use multiple threads can the total memory bandwidth get limiting. So as much as I would love faster ram in my uses where I know it has a benefit, pricing one you get to the 3000's starts to climb rapidly. Unless you know you have something that benefits it, I wouldn't recommended getting the fastest. If you do, you'll never have to worry about it again, but I'm also a bit cautious about compatibility of the fastest speeds. Otherwise, the low 3000's is more reasonably priced and yet still gives a good boost above basic speeds.

Well, the last video that HKZeroFive posted shows significant improvements with CPU bound games on the 7770K specifically but they did only go up to 3000. It looks like the price doesn't really start jumping too much until after 3600 though so maybe 3600 is the sweet spot although 3000 and 3200 actually seem to be topping the benchmarks right now but no one seems to have benchmarked anything above 3600 on the site I was looking at and there aren't really too many samples of even the 3000 or 3200. 

[porina]

1 minute ago, eric6 said:

Well, the last video that HKZeroFive posted shows significant improvements with CPU bound games on the 7770K specifically but they did only go up to 3000. It looks like the price doesn't really start jumping too much until after 3600 though so maybe 3600 is the sweet spot although 3000 and 3200 actually seem to be topping the benchmarks right now but no one seems to have benchmarked anything above 3600 on the site I was looking at and there aren't really too many samples of even the 3000 or 3200. 

I only own ram rated up to 3333 myself, although with the new Trident Z RGB starting to become available I'm debating getting some faster and flashier stuff. For 100% stability I find subtle compatibility problems start above 3000 or so, which is in part why I'm hesitant to recommend it on top of the pricing.

 

I also suspect there is a contributor from ram rank in conjunction with ram speed, which as far as I'm aware hasn't been explored in a gaming context. Now I think about it... that could be my job after lunch.