PDA

View Full Version : [SOLVED] 11.04 - recognises only half of Bulldozer CPU cores



VinisLentoje
January 16th, 2012, 09:29 PM
Hello!

So, I had a major hardware upgrade today. It includes upgrading my CPU to an 8-core Bulldozer (AMD FX 8120).
After I booted into my ubuntu installation (11.04|natty; x64; 2.6.38-13-generic), I noticed that only four [half] of the cores are recognised by the kernel.
Is this normal? Considering the structure of the Bulldozer architecture, I suppose this could be intentional on the kernel side. Thus, I'm wondering which is the case:
#1 the kernel wrongfully detects and uses only half of the cores,
or
#2 the kernel detects that the CPU is module-based, and exposes each core pair as one, but actually "fills"/uses both cores on a module?
Reading through the kern.log makes me lean onto #1, as it does not mention anything on that matter. And I suppose the kernel would inform about it.

P.S. I tried googling this, but 99% of the results were discusions & blog posts that jumped on that whole "Bulldozer is horrible" bandwagon thing. [I guess most of the people bashing it never actually used it. Pffff...]
And also, I could not find anything relevant by searching this forum. So, I'm really sorry, if this was posted before, but slipped through my "radar".

spacecheck
January 16th, 2012, 09:50 PM
Might want to ask that question here:
http://blogs.amd.com/work/2011/05/16/stop-the-clocks/
AnandTech about Windoze using (trying to use) option #2:
http://www.anandtech.com/show/5251/microsoft-releases-hotfix-to-improve-bulldozer-performance

Good luck!

VinisLentoje
January 16th, 2012, 10:14 PM
Might want to ask that question here:
http://blogs.amd.com/work/2011/05/16/stop-the-clocks/
AnandTech about Windoze using (trying to use) option #2:
http://www.anandtech.com/show/5251/microsoft-releases-hotfix-to-improve-bulldozer-performance

Good luck!

Even though I already read those two articles a while ago, Thanks!

I guess I should include a couple of more detailed questions. Those might help figure this thing out.

I did not see this directly, but from various things I read on the net, I have an impression that the 3.0 and later kernels detect and expose all the cores. That's why I asked if my case is normal. Thus: on the 3.0 and later kernels - which way is it detected and exposed: #1. 2 cores for every module[containing 2 "cores"] (as the CPU is "supposed" to be), or #2. as 1 core for every module (some sort of virtualization by the kernel or something]. If the answer is #1, then I probably need to get a newer kernel.

In other words - should I get a new kernel somehow, or is it ok as it is now?

spacecheck
January 16th, 2012, 10:50 PM
Put in a LiveCd for 11.10, as a test, since it uses 3.0.0.14. You will then discover what the bulldozer 'sees'. I mentioned the AMD-link, because you could ask the author via his blog...

Good luck!

VinisLentoje
January 17th, 2012, 12:20 AM
Aww, shucks! It appears using 1-core/1-module was set by default in my BIOS. Took me a while to notice =/
Sorry about that...
I guess I'll just go and smack my face into the nearest pine tree [whatAnIdiot]. ~_~