The Phenom / PhenomII memory controller: ganged vs unganged mode benchmarked

Written by Gionatan Danti on . Posted in Hardware analysis

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Synthetic benchmarks: MEMBENCH sparse memory speed

What about single process sparse (semi-random) memory access?

MEMBENCH random memory speed - one process

Well, we see a common picture: the read test execute faster on ganged configuration, while the other test benefit from the unganged mode.

Now, let's see what happen if two processes use sparse (semi-random) memory access:

MEMBENCH random memory speed - two processes

The read advantage of ganged mode is almost vanished, while the advantage of unganged configuration in write and mixed (copy) test grow.

In the end, let's look at the performance of the concurrent (a reading and a writing processes) sparse memory access

MEMBENCH random memory speed - concurrent read/write operations

Quite surprisingly, the score are practically tied.

These tests show that, based on the access pattern to main memory, the ganged mode can be either faster or slower than unganged mode, and vice versa. However, it seems that unganged mode win more tests that it loses, so it seems the preferred memory controller configuration.

Comments   

 
#1 Julián Fernández 2012-07-21 00:40
This was quality reading. Thanks mate.
 
 
#2 Iz 2013-01-24 23:14
Thank you for sharing these insights. I found them most useful indeed.
 
 
#3 asd 2014-03-26 19:17
Your graphs are misleading. You should ALWAYS show the full range in any graph (i.e. starting at 0 value), so the magnitude of the gains can be seen at first glance. This is statistics 101.
At least you labeled your axis.
 
 
#4 Gionatan Danti 2014-03-26 19:29
Quoting asd:
Your graphs are misleading. You should ALWAYS show the full range in any graph (i.e. starting at 0 value), so the magnitude of the gains can be seen at first glance. This is statistics 101.
At least you labeled your axis.


Yes, you are right.

When the differences are small, old OpenOffice Calc versions tend to create graphs which don't start from 0.

I realized that only after the graph were published, and I preferred to leave them unmodified.

Regards.
 
 
#5 Jay 2016-06-06 07:09
Thank you for this in-depth piece. It was the best explanation I've come across, and I've been looking for a while. :)
 
 
#6 SvenBent 2016-08-20 16:11
Ncie read through but really wish the bar graphs wasn;t made so misleading. now i have t ohave a huge focus on et he X-axis to get a indication of how big the diffrent really is.

really bad to not start your graphs at 0
 

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