mersenneforum.org

mersenneforum.org (https://www.mersenneforum.org/index.php)
-   Hardware (https://www.mersenneforum.org/forumdisplay.php?f=9)
-   -   Which DDR4 RAM is best for LL on intel CPUs? (https://www.mersenneforum.org/showthread.php?t=23718)

simon389 2018-10-22 18:41

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 ([URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16811353095"]link[/URL])

CPU: Intel Core i7-9700K Coffee Lake 8-Core 3.6 GHz ([URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16819117958"]link[/URL])

Mobo: MSI MPG Z390I GAMING EDGE AC ([URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16813144215"]link[/URL])

RAM: G.SKILL TridentZ RGB Series 32GB (2 x 16GB) DDR4 3866Mhz ([URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16820232606"]link[/URL])

Note: 3866mhz RAM has been approved for this mobo

PSU: SeaSonic 400W Platinum ([URL="https://www.newegg.com/Product/Product.aspx?Item=N82E16817151097"]link[/URL])

Cooler: ArcticCooling Freezer i32 ([URL="https://www.newegg.com/Product/Product.aspx?Item=9SIA4RE4M24012"]link[/URL])

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 2018-10-22 19:14

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 2018-10-22 19:25

[QUOTE=Mark Rose;498509]Haswell (4000 series) or better though. You'll get much more throughput/watt.[/QUOTE]

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 2018-10-22 19:52

[QUOTE=VBCurtis;498527]TIf you plan on Prime95 or LLR, you'll have 4 idle cores and an utterly wasted expensive CPU.[/QUOTE]

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 2018-10-22 20:13

[QUOTE=irowiki;498529]It figures you would say that as I was looking at a bunch of cheap ivy bridge i5-3470s![/quote]

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.

[quote]
My favorite in my whole lineup are my machines with the i5-4590, that thing moves![/QUOTE]

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

irowiki 2018-10-23 18:19

[QUOTE=Mark Rose;498533]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.[/quote]

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.


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

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 2018-10-23 20:03

[QUOTE=irowiki;498592]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.[/quote]

Not a bad price.

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

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

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

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 2018-10-24 04:18

[QUOTE=Mark Rose;498604]Yeah. Basically, the CPUs are busy enough to stay fully clocked, but are still waiting on memory.[/quote]

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





[quote]
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.[/QUOTE]

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 2018-10-25 21:59

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 2018-10-25 23:52

[QUOTE=Brandon;498752]Is this simply a case of RAM being a bottleneck? [/QUOTE]

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 2018-10-26 03:27

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


All times are UTC. The time now is 16:39.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.