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Memory power management power savings testMemory power management power savings testPosted Jun 10, 2011 16:20 UTC (Fri) by etienne (subscriber, #25256)In reply to: Memory power management power savings test by ccurtis Parent article: Memory power management
Maybe just reboot your PC with different number of memory modules and measure the power difference?
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Memory power management power savings test Posted Jun 11, 2011 3:19 UTC (Sat) by willy (subscriber, #9762) [Link]
The problem is that pages are interleaved across DIMMs. If you have 3 channels with a single DIMM each, cacheline 0 is on DIMM 0, cacheline 1 on DIMM 1, cacheline 2 on DIMM 2 and cacheline 3 on DIMM 0. Removing a DIMM causes the interleaving to change, which will also cause performance to change, and your measurements are now invalid.
As I understand PASR, one would not power down an entire DIMM, but rather sections of each DIMM, thus preserving the performance benefits of interleaving.
Memory power management power savings test Posted Jun 16, 2011 4:54 UTC (Thu) by Ankita (subscriber, #39147) [Link]
Yes, PASR support seems to be at bank level. From a few documents I have read, I find that interleaving can be configured to control the number of banks that have to be kept open for every memory access, typically the minimum being 2 banks. Thus, if only two banks are interleaved, the other banks can potentially be turned off or not refreshed. Power v performance benchmarking will be needed to decide on the best interleaving scheme though.
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