From: Mikael Pettersson <mikpe@csd.uu.se>
To: mru@kth.se (Måns Rullgård)
Cc: linux-kernel@vger.kernel.org
Subject: Re: hyperthreading
Date: Tue, 25 Nov 2003 11:45:05 +0100 [thread overview]
Message-ID: <16323.12977.677299.198663@alkaid.it.uu.se> (raw)
In-Reply-To: <yw1xptfgd9hc.fsf@kth.se>
Måns Rullgård writes:
> Gábor Lénárt <lgb@lgb.hu> writes:
>
> >> > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> >> > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
> >> > bogomips : 3334.14
> >>
> >>
> >> P4 does not support HT ... only Xeon and new generation P4-HT does.
> >
> > OK, but if this CPU does not support HT, then why 'ht' is shown at
> > flags in /proc/cpuinfo? It looks like quite illogical for me then ...
>
> I've been wondering about that myself. I'm sure my P4M doesn't have
> any hyperthreading.
Don't people read Intel docs any more?
- The HT feature flag means "might have HT, check further to make sure".
- "check further" involves checking #siblings >= 2 via CPUID.
Old P4s typically announce HT but have #siblings < 2.
- Intel made HT enabling a hardware thing via the chipset (a pin
sampled at reset). BIOS can disable HT but only HW can enable it.
This is why you can't put a HT-capable P4 in a non-HT-chipset
machine and expect it to work -- although PowerLeap seemed to
have an adapter to "fix" that.
next prev parent reply other threads:[~2003-11-25 10:46 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-25 9:44 hyperthreading Gábor Lénárt
2003-11-25 9:48 ` hyperthreading Emiliano 'AlberT' Gabrielli
2003-11-25 10:05 ` hyperthreading Gábor Lénárt
2003-11-25 10:16 ` hyperthreading Arjan van de Ven
2003-11-25 10:32 ` hyperthreading Måns Rullgård
2003-11-25 10:45 ` Mikael Pettersson [this message]
2003-11-29 13:29 ` hyperthreading Bill Davidsen
2003-12-01 10:53 ` hyperthreading Emiliano 'AlberT' Gabrielli
2003-11-25 10:22 ` hyperthreading Karl Pitrich
-- strict thread matches above, loose matches on Subject: below --
2002-08-22 12:58 Hyperthreading Nir Soffer
2002-08-22 14:30 ` Hyperthreading Hugh Dickins
2002-08-22 9:15 Hyperthreading Marc Dietrich
2002-08-22 14:06 ` Hyperthreading Hugh Dickins
2002-08-22 14:36 ` Hyperthreading Marc Dietrich
2002-08-21 22:56 Hyperthreading Nakajima, Jun
2002-08-21 23:45 ` Hyperthreading Alan Cox
2002-08-21 11:32 Hyperthreading Reed, Timothy A
2002-08-21 13:48 ` Hyperthreading James Bourne
2002-08-21 17:33 ` Hyperthreading Hugh Dickins
2002-08-21 19:34 ` Hyperthreading James Bourne
2002-08-21 21:16 ` Hyperthreading Kelsey Hudson
2002-08-21 21:55 ` Hyperthreading Banai Zoltan
2002-08-22 8:05 ` Hyperthreading venom
2002-08-26 19:00 ` Hyperthreading Kelsey Hudson
2002-08-22 8:00 ` Hyperthreading venom
2002-08-23 7:28 ` Hyperthreading Gilad Ben-Yossef
2002-08-23 8:10 ` Hyperthreading Hugh Dickins
2002-08-23 8:27 ` Hyperthreading Alan Cox
2002-08-23 8:12 ` Hyperthreading venom
2002-04-18 1:52 Hyperthreading Holzrichter, Bruce
2002-04-17 20:34 Hyperthreading Holzrichter, Bruce
2002-04-17 22:48 ` Hyperthreading Martin J. Bligh
2002-04-18 1:21 ` Hyperthreading James Bourne
2002-04-17 20:02 SMP P4 APIC/interrupt balancing James Bourne
2002-04-17 21:10 ` Hyperthreading Martin J. Bligh
2002-04-17 20:15 ` Hyperthreading Robert Love
2002-04-17 20:23 ` Hyperthreading Dave Jones
2002-04-17 21:24 ` Hyperthreading Jeff V. Merkey
2002-04-17 20:25 ` Hyperthreading James Bourne
2002-04-17 21:26 ` Hyperthreading Jeff V. Merkey
2002-04-18 0:31 ` Hyperthreading Martin J. Bligh
2002-04-18 4:50 ` Hyperthreading Jeff V. Merkey
2002-04-17 22:12 ` Hyperthreading Alan Cox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=16323.12977.677299.198663@alkaid.it.uu.se \
--to=mikpe@csd.uu.se \
--cc=linux-kernel@vger.kernel.org \
--cc=mru@kth.se \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®