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Old 2019-10-15, 16:54   #1
wildrabbitt
 
Jul 2014

3×149 Posts
Default possible purchase of memory.

Thinking about buying this :



https://www.grooves-inc.co.uk/skill-skill-16gb-ddr4-3200-ddr4-3200mhz-memory-module-skill-accessories-pZZa1-2097716466.html?language=en¤cy=GBP&utm_source=froogle_gb&utm_campaign=froogle_gb&gclid=Cj0KCQjw3JXtBRC8ARIsAEBHg4myn9NP_03SAjWvL5rT-iFNNDN2IzdrOzb4uvFQ9fibXcNnf-lqABIaApJgEALw_wcB


I've got two questions. The setup is


i3-8350K CPU @ 4.00GHz × 4

Ubuntu 18.04.2 LTS 64-bit


I've got 2 8GB sticks of G Skill F4-3200C 16D-16GTZB DDR4-3200 Trident Z


I get about 12.2ms running two Lucas Tests with exponents around 87073397 (for example).


My first question would having 32GB instead of 16 speed things up?

My second question is : will the memory I'm considering buying be compatible with the memory I've got. I'm wondering because the manufacturing model number is slightly different.


Advise please.

Last fiddled with by wildrabbitt on 2019-10-15 at 16:54
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Old 2019-10-15, 17:28   #2
hansl
 
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Apr 2019

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That CPU has a max 2 memory channels, so I don't think you would benefit from 4 sticks in terms of bandwidth.

Quote:
Originally Posted by https://ark.intel.com/content/www/us/en/ark/products/126689/intel-core-i3-8350k-processor-8m-cache-4-00-ghz.html
Max # of Memory Channels 2
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Old 2019-10-15, 18:42   #3
ewmayer
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Sep 2002
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Just got a "huge sale!!!" e-mail from Newegg.com, might be worth checking out, of for nothing else but comparison-shopping.
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Old 2019-10-15, 19:16   #4
mackerel
 
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Feb 2016
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You're probably ram bandwidth limited running that CPU stock. Going to 4 modules helps by you having 2DPC. I have no idea why it helps, but it does. Same effect as dual rank modules. Effect can be significant, tens of %.

Can't be certain on compatibility. It'll probably be ok.

Last fiddled with by mackerel on 2019-10-15 at 19:17
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Old 2019-10-15, 20:36   #5
wildrabbitt
 
Jul 2014

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Quote:
You're probably ram bandwidth limited running that CPU stock.

You mean I can use four RAM sticks? Is there something in the BIOS I need to change or would two extra sticks work as is?
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Old 2019-10-15, 20:56   #6
hansl
 
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Apr 2019

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If you want to be extra cautious, you can see if your motherboard manufacturer provides a QVL (Qualified Vendor List) for which RAM modules are compatible with your specific mobo model.
Although as I understand it, RAM compatibility is less of a concern on Intel than with AMD/Ryzen for example.

Also, maybe obvious, but have you made sure to enable XMP in BIOS so you get the most out of the RAM you already have?
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Old 2019-10-15, 21:22   #7
mackerel
 
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What motherboard do you have? I'm assuming it has 4 slots, so then it could use 4 sticks. No specific setting for 4 sticks, but as hansl mentioned you probably need to turn on XMP to get it running at rated speed if not done already.

There will still be some risk on compatibility. The QVL in general I find little use as they can't test every module available, they certainly wont test mixed modules, and ram module manufacturers can change design without changing product name.
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Old 2019-10-15, 21:43   #8
wildrabbitt
 
Jul 2014

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Quote:
Also, maybe obvious, but have you made sure to enable XMP in BIOS so you get the most out of the RAM you already have?

Yup.


Thanks for all that chaps. I can make an informed decision now.
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Old 2019-10-18, 05:03   #9
NookieN
 
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Quote:
Originally Posted by wildrabbitt View Post
I get about 12.2ms running two Lucas Tests with exponents around 87073397 (for example).
That sounds a little slow. One of my systems is nearly identical except the CPU is an older 6700K at 4GHz. It gets 5.5ms on that same exponent range (1 worker). I would expect two workers to be fairly close to 11ms.
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