Comprehensive Threadripper tests - memory vs cpu freq at capped power
M. L. Wilson
ipc at peercorpstrust.org
Fri Aug 24 03:38:45 PDT 2018
Many thanks for this explanation!
On 08/24/2018 03:04 AM, Gerald Henriksen wrote:
> On Thu, 23 Aug 2018 23:17:29 +0300, you wrote:
>> The Threadripper discussion has been very interesting.
>> Will these adjustments to NUMA for Threadripper's topography also apply to Epyc also? Or will more nuanced work need to be done once an Epyc system becomes available?
> Epyc doesn't have the limitations that Threadripper has, so the
> changes aren't needed.
> The basic explanation is this.
> With both Threadripper and Epyc the module you plug into the
> motherboard actually contains 4 chips, connected together.
> Each chip has 2 memory controllers.
> In Epyc all 4 chips have their memory controllers enabled/connected,
> thus allowing each chip to access memory directly.
> With the original version of Threadripper only 2 of the 4 chips were
> active, and the 2 active chips had their memory controllers enabled
> allowing direct access.
> The new version of Threadripper has all 4 chips active BUT only 2
> chips have memory controllers enabled. Thus the 2 chips without
> active memory controllers are forced to access memory through the
> other 2 chips. This is what is requiring the changes.
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