trouble with HT

Jonathan Horne freebsd at
Wed Apr 4 02:25:35 UTC 2007

On Tue, 3 Apr 2007 20:57:21 -0400
Kris Kennaway <kris at> wrote:

> On Tue, Apr 03, 2007 at 07:45:55PM -0500, Jonathan Horne wrote:
> > building a new system, processor is:
> > 
> > CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2793.20-MHz 686-class CPU)
> >   Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
> > TM,PBE>
> >   Features2=0x4400<CNTX-ID,<b14>>
> > 
> > and the chipset is Intel 865G.  in 6.2, the old method of enabling HT with sysctl.conf seems to be depricated, as i got a nastygram from dmesg that im a dummy on boot up (so i took those back out).  then i read thru some docs, and apparently, HT is supposed to be enabled in the base release now.
> > 
> > strange part is, for a while, 'top -C' would show me the C column, and i actually could see some 0's and 1's, so i went about my business of building ports.  now that i go back, the -C is no longer being obeyed, and i cant get the C column to appear.
> That suggests you may have rebuilt your kernel without SMP support.
> > how can i verify that HT is working?  my mobo (IBM 8189) doesnt seem to have an on/off for HT, so my first inclenation is assume that its on (we have many windows machines running on this hardware, and HT never seems to be a problem with those).
> > 
> > any pointers would be appreciated (and yes, already know alllll about the security advisories... :)
> And about the possible poor performance I assume :)
> Kris
> _______________________________________________

well, wikipedia says this (something that i just now learned about standard pentium4 line of processors)
The 3.06 GHz processor supported Hyper-Threading (first appeared in Xeon), enabling multiple threads to be run together by duplicating some parts of the processor in order to let the operating system believe that there are two logical processors. HyperThreading was present in all Northwood CPUs, but was disabled in the core in all but the 3.06 GHz model.

until now, my only pentium 4 was a 3.2 which does, and some 1.8s which i already knew didnt support it.  i guess i just figured that my xeons at 533 FSB supported, it, xeons at 400FSB supported, it... so a 2.8 with 533 should support it too??  oh well, not if its disabled in the core.  (jonathan makes a sad face)


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