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Date:      Fri, 31 Jan 2003 15:59:00 -0500 (EST)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        Matthew Dillon <dillon@apollo.backplane.com>, Trish Lynch <trish@bsdunix.net>, freebsd-current@FreeBSD.ORG, "Daniel C. Sobral" <dcs@tcoip.com.br>
Subject:   Re: Hyperthreading and machdep.cpu_idle_hlt
Message-ID:  <XFMail.20030131155900.jhb@FreeBSD.org>
In-Reply-To: <Pine.BSF.4.21.0301311241170.45015-100000@InterJet.elischer.org>

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On 31-Jan-2003 Julian Elischer wrote:
> 
> 
> On Fri, 31 Jan 2003, John Baldwin wrote:
> 
>> >> AT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,<b28>,ACC>
>> >> 
>> >>     It has HTT set but it's only a 1.2GHz box and I heard somewhere that only
>> >>     2+ GHz P4's had hyperthreading.  I noticed some MFCs to stable that 
>> >>     suggested hyperthreading support but I do not know if full hyperthreading
>> >>     support has been MFCd yet or is intended to be MFCd to -stable.
>> > 
>> > AFAIK, full hyperthreading support, as it is, has been merged to 
>> > -stable. It consists of a patch to recognize the virtual CPUs, so they 
>> > will be dealt with like any SMP system, as long as HTT is enabled on the 
>> > BIOS.
>> 
>> Well, sort of.  We have no way of knowing if it is off in the BIOS unless
>> we use the ACPI tables to enumerate CPU's (which we don't), so turning it
>> off in the BIOS won't turn it off in FreeBSD for the time being. :)
>> 
> I have a 2,8GHz p4 here which has HTT and has a bios option for 
> 
> Interrupt mode: [APIC/PIC]
> 
> I'm using APIC mode but an SMP (today's 4.x) kernel
> panics imediatly saying it can;t find an APIC.

You need to have an mptable for it to work.  The mptable will
only list one processor, but it still needs to be there.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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