Which DDR4 RAM is best for LL on intel CPUs?

[simon389]

Let me clarify why I'm going with 3 enthusiast machines and not 5-8 consumer machines. I don't want a ton of heat being produced in my basement. I just want to keep things small and orderly. So I'd rather have three really fast machines even if it costs more.

I ended up buying:

Case: DIYPC DIY-F2-O Black/Orange USB 3.0 Micro-ATX Mini Tower (link)

CPU: Intel Core i7-9700K Coffee Lake 8-Core 3.6 GHz (link)

Mobo: MSI MPG Z390I GAMING EDGE AC (link)

RAM: G.SKILL TridentZ RGB Series 32GB (2 x 16GB) DDR4 3866Mhz (link)

Note: 3866mhz RAM has been approved for this mobo

PSU: SeaSonic 400W Platinum (link)

Cooler: ArcticCooling Freezer i32 (link)

SSD (w/ Windows 7): Old 240GB I have laying around

Total cost: $1300


Problem: I realize now that I got a dual-channel RAM setup, when Skylake-X has quad-channel RAM. If this will result in slower LL crunching, should I return everything and get a quad-channel setup considering RAM is the biggest bottleneck?

[VBCurtis]

Two channels of DDR4 are maxed out by 4 cores. So, if you have something that isn't memory-bandwidth-intensive for the other 4 cores to do, your setup is fine. If you plan on Prime95 or LLR, you'll have 4 idle cores and an utterly wasted expensive CPU.
Your memory speed might allow you to get 4.5 cores worth of production, but you really really need quad channel and 4 memory sticks for that CPU.

[irowiki]

Originally Posted by Mark Rose

Haswell (4000 series) or better though. You'll get much more throughput/watt.

It figures you would say that as I was looking at a bunch of cheap ivy bridge i5-3470s!

My favorite in my whole lineup are my machines with the i5-4590, that thing moves!

[mackerel]

Originally Posted by VBCurtis

TIf you plan on Prime95 or LLR, you'll have 4 idle cores and an utterly wasted expensive CPU.

If LLR, the CPU could still be interesting. "Smaller" tasks could fit in the L3 cache and not be ram bandwidth limited. Above that, bandwidth is king, even a 6 core quad channel would likely out perform the 8 core dual channel setup.

[Mark Rose]

Originally Posted by irowiki

It figures you would say that as I was looking at a bunch of cheap ivy bridge i5-3470s!

That chips shouldn't be too bad, actually, if it's coupled with DDR3-1600. But keep in mind a new i3-8100 with dual rank DDR-2400 will be something like twice as power efficient.

My favorite in my whole lineup are my machines with the i5-4590, that thing moves!

That one is certainly bottlenecked by its maximum clocked DDR3-1600 RAM. I'd look at underclocking/undervolting it.

[irowiki]

Originally Posted by Mark Rose

That chips shouldn't be too bad, actually, if it's coupled with DDR3-1600. But keep in mind a new i3-8100 with dual rank DDR-2400 will be something like twice as power efficient.

Ah, dude has a few dozen dell mini towers leftover from bitcoin mining and he wants $100 for each, was going to try and strike a deal for five or so if they were worth it.

That one is certainly bottlenecked by its maximum clocked DDR3-1600 RAM. I'd look at underclocking/undervolting it.

Interesting. So even though it's maxing every core out, it's "wasting" energy so to speak?

It's interesting because I have a new Dell with an i5 6500 and the 4590 beats it handily.

[Mark Rose]

Originally Posted by irowiki

Ah, dude has a few dozen dell mini towers leftover from bitcoin mining and he wants $100 for each, was going to try and strike a deal for five or so if they were worth it.

Not a bad price.

Interesting. So even though it's maxing every core out, it's "wasting" energy so to speak?

Yeah. Basically, the CPUs are busy enough to stay fully clocked, but are still waiting on memory.

It's interesting because I have a new Dell with an i5 6500 and the 4590 beats it handily.

Almost certainly comes down to either insufficient cooling on the 6500, or the memory configuration. I have a bunch of i5-6600 that I disable turbo on, then undervolt a lot. Why? They're limited to 4 ranks of DDR4-2133, so going any faster than 3.3 GHz is pointless.

I also have a 4770k system with 8 ranks of DDR4-2400 that's faster than the 6600's.

[irowiki]

Originally Posted by Mark Rose

Yeah. Basically, the CPUs are busy enough to stay fully clocked, but are still waiting on memory.

Ah, I shall look into it, but not sure if you can undervolt a stock Dell.

Almost certainly comes down to either insufficient cooling on the 6500, or the memory configuration. I have a bunch of i5-6600 that I disable turbo on, then undervolt a lot. Why? They're limited to 4 ranks of DDR4-2133, so going any faster than 3.3 GHz is pointless.

I also have a 4770k system with 8 ranks of DDR4-2400 that's faster than the 6600's.

Not a cooling issue I wouldn't think, it was doing the same when it first started and an hour later, also it's an Optiplex and has overkill cooling. I'm guessing it's just cheap motherboard/memory issues.

[Brandon]

So this seems like a good place to ask a RAM related question at the moment.

I have a Dell Inspiron 15 7000 Gaming laptop, running an i7-7700HQ, with 8GB DDR4 2400, just one stick, so single channel.

I've noticed when running an LL exponent(1 exponent, 4 cores), in any range, the difference in ms/iter between 2.8 GHz(power saving mode) and 3.8 GHz(high performance mode), is practically none. 3.8GHz is no faster, and of course just gets hotter(though I have done some undervolting to help thermals)

Is this simply a case of RAM being a bottleneck?
Probably a really obvious question, I just want to be sure. I see no other explanation...
(sorry if this is not the appropriate place to ask this, 'tis my first post!)

[Prime95]

Originally Posted by Brandon

Is this simply a case of RAM being a bottleneck?

Yes.

I think it a case of gross negligence that Dell would sell a laptop with that memory configuration (esp. calling it a "Gaming" laptop). Single channel RAM will impact all applications you run.

[Brandon]

Well darn. I'll have to order a matching stick at some point. Thanks for confirming that though.