dmccunney composed on 2021-03-11 09:51 (UTC-0500):

> Felix Miata wrote:

>> Odds are that 32GB capable board features dual channel RAM.
>> https://en.wikipedia.org/wiki/Multi-channel_memory_architecture

> Possible.

>> IME when RAM is not used in matched pairs in correct slots in a dual channel
>> board, RAM speed (memtest86) is cut by nearly half. Did you test RAM speed 
>> before
>> and after the change?

> No.  I simply made sure I had RAM that matched the specs of the other
> sticks.  The only difference was that one stick is 8GB instead of
> four. I was *not* using RAM of different speeds, and no mismatch was
> involved..

> I saw *no* negative performance impact, and would have been startled if I did.
                                                                                
By not matching size of pairs, you disable dual channel. You should run 
memtest86
with and without the 4G and 8G sticks to see the difference in print on your 
screen.

A quick test here using MemTest86 V8.3 Free on:

CPU: AMD A10-7850K Radeon R7, 3.7Ghz
motherboard: ASUSTeK model: A88X-PRO
RAM: Mushkin DDR3-2133 XMP, 10-12-12-28, 2 sticks of 4GB each
matched pair RAM speed: 7474 MB/s dual channel
single stick RAM speed: 5943 MB/s not dual channel = 79.5%

CPU: Intel Pentium G4600, 3.6GHz
motherboard: ASUSTeK model: B85M-E
RAM: Crucial DDR4-2400, 17-17-17-39, 2 sticks of 8GB each
matched pair RAM speed: 21.67 GB/s dual channel
single stick RAM speed: 13.92 GB/s not dual channel = 64.2%
RAM: generic DDR4-2400, 17-17-17-39, 2 sticks of 8GB each
matched pair RAM speed: 19.92 GB/s dual channel
single stick RAM speed: 12.07 GB/s not dual channel = 60.6%

My recollection is with DDR2 the difference tended to be bigger, as low as 53% 
for
1 stick compared to dual channel.
-- 
Evolution as taught in public schools, like religion,
        is based on faith, not on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/


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