linux-kernel - Re: ht CPU flag

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Message-ID: <Pine.LNX.4.64.0705190858590.29910@ns.armcci.am>
Date:	Sat, 19 May 2007 10:18:20 +0500 (AMST)
From:	eugene@...armcci.am
To:	Chris Snook <csnook@...hat.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: ht CPU flag

On Fri, 18 May 2007, Chris Snook wrote:

> eugene@...armcci.am wrote:
>>
>>
>>  On Fri, 18 May 2007, Chris Snook wrote:
>> 
>> >  eugene@...armcci.am wrote:
>> > >   --------------------------------------------------------------------------- 
>> > > 
>> > > 
>> > >   I have Pentium D CPU, which many Windows utilities like cpuz, wcpuid,
>> > >   everest identify as D 930 (Dual Core, 3GHz). From Intel site I find 
>> > >   out
>> > >   that it has no HT feature, nor Windows XP identify it as HT.
>> > > 
>> > >   Why do I have "ht" flag in cpuinfo?
>> > >   -----------------------------------
>> > 
>> >  The "ht" flag merely means "I know how to report hyperthreaded logical 
>> >  processors if I have them."  My Woodcrest Xeon 5110 and my Athlon64 X2 
>> >  both have the "ht" flag, and correctly report the zero hyperthreaded 
>> >  logical processors they each have.
>> > 
>> >      -- Chris
>> > 
>> >
>>
>>  Thanks, Chris.
>>
>>  Am I right that is chipset on mainboard, who is saying - "I know....", not
>>  CPU itself? Is it better to switch off HT support in BIOS?
>>  Is it possible to generate CPU name as: "Pentium D 930" in /proc/cpuinfo?
>>  On the other server I have some 2GHz HT Xeons which can't be identified on
>>  Intel site because of strange naming pattern.
>>  I tried to find any utility for Linux to solve this, but it looks like
>>  everybody are using /pros/cpuinfo, which is not enough :)
>>
>>  Regards, Eugene.
>
> While the BIOS can disable HT, the ability to *report* HT or the lack thereof 
> is within the CPU itself.  I doubt my socket AM2 board has the faintest clue 
> what HT is.
>
> As for human-readable names, the model name in /proc/cpuinfo comes from the 
> processor name string, and includes however much or little information the 
> vendor thinks the lay user wants to know.  If you want more detail, you can 
> always interpret the model, stepping, and other related fields to determine 
> the model number.
>
> If you don't want to manually look up model info on a CPU version table, 
> x86info and dmidecode will give you more information.
>
> 	-- Chris
>

As I already told, there is no stepping 4 for Xeons on Intel site! So 
/proc/cpuinfo, dmidecode, x86info are all wrong.
Moreover, x86info is too old and can't work with /sys fs.

Also Linux is poor on giving FSB and Memory frequency, which I need to be 
sure that memory timing is correct (SPD gives slower parameters then are 
on SDRAM labels :( ).
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