Re: What processor features does Guix support on i686?

Re: What processor features does Guix support on i686?

[Joshua Branson]

This email list was posted on guix-devel, I'm asking this question on
help-guix, because it's a help guix question and not a guix devel
question...

Mark H Weaver <mhw@netris.org> writes:

> Hi Leo,
>
> Thanks for asking about this, and for ably taking care of our
> Linux-libre packages.  I'm grateful for your work on this.
>
> Leo Famulari <leo@famulari.name> writes:
>
>> I noticed that Linux 5.12 has a new config option regarding "Processor
>> family". The default choice, Pentium-Pro (M686), is highlighted in this
>> quote:
>>
>> ------
>> Processor family
>>   1. 486SX (M486SX) (NEW)
>>   2. 486DX (M486) (NEW)
>>   3. 586/K5/5x86/6x86/6x86MX (M586) (NEW)
>>   4. Pentium-Classic (M586TSC) (NEW)
>>   5. Pentium-MMX (M586MMX) (NEW)
>>> 6. Pentium-Pro (M686) (NEW)
>>   7. Pentium-II/Celeron(pre-Coppermine) (MPENTIUMII) (NEW)
>>   8. Pentium-III/Celeron(Coppermine)/Pentium-III Xeon (MPENTIUMIII) (NEW)
>>   9. Pentium M (MPENTIUMM) (NEW)
>>   10. Pentium-4/Celeron(P4-based)/Pentium-4 M/older Xeon (MPENTIUM4) (NEW)
>>   11. K6/K6-II/K6-III (MK6) (NEW)
>>   12. Athlon/Duron/K7 (MK7) (NEW)
>>   13. Opteron/Athlon64/Hammer/K8 (MK8)
>>   14. Crusoe (MCRUSOE) (NEW)
>>   15. Efficeon (MEFFICEON) (NEW)
>>   16. Winchip-C6 (MWINCHIPC6) (NEW)
>>   17. Winchip-2/Winchip-2A/Winchip-3 (MWINCHIP3D) (NEW)
>>   18. AMD Elan (MELAN) (NEW)
>>   19. GeodeGX1 (MGEODEGX1) (NEW)
>>   20. Geode GX/LX (MGEODE_LX) (NEW)
>>   21. CyrixIII/VIA-C3 (MCYRIXIII) (NEW)
>>   22. VIA C3-2 (Nehemiah) (MVIAC3_2) (NEW)
>>   23. VIA C7 (MVIAC7) (NEW)
>>   24. Core 2/newer Xeon (MCORE2)
>>   25. Intel Atom (MATOM)
>> ------

I'm kind of curious, if I were to compile my own linux kernel, and I
could someone select a newer processor family, would that make my kernel
a little more faster?  Or would it just make my kernel image a little
smaller?  Also my laptop is a Lenovo T400.    So it doesn't exactly have
NEW features.  :)

>>
>> info: https://cateee.net/lkddb/web-lkddb/M686.html
>>
>> I know that, in the past, we have been careful to not require certain
>> processor features on i686, such as SSE [0].
>>
>> I would appreciate some guidance, both about this kernel configuration
>> option, and what we have historically considered to be the "minimum
>> requirements" for i686 hardware. I will put that information the manual
>> so that it doesn't get lost.
> [...]
>> [0] https://lists.gnu.org/archive/html/guix-devel/2016-07/msg01534.html
>
> It's been a long while since I looked at this, and of course we may wish
> to revisit the issue, but for now, I think that the right choice above
> is the default one, namely: "6. Pentium-Pro (M686) (NEW)"
>
>    Thanks again,
>        Mark

--
Joshua Branson (joshuaBPMan in #guix)
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enough other people get what they want." - Zig Ziglar

Re: What processor features does Guix support on i686?

[Leo Famulari]

On Sun, May 02, 2021 at 12:56:45PM -0400, Joshua Branson wrote:
> I'm kind of curious, if I were to compile my own linux kernel, and I
> could someone select a newer processor family, would that make my kernel
> a little more faster?  Or would it just make my kernel image a little
> smaller?  Also my laptop is a Lenovo T400.    So it doesn't exactly have
> NEW features.  :)

Just to clarify, these kernel configuration options are for when one
builds the kernel for "i686-linux" (Guix parlance) or "i386" (Linux
parlance). This means 32-bit Intel-compatible.

The T400 has a Core 2 Duo 64-bit procesor, so these options won't apply
for you. That's "x86_64-linux" or "amd64", respectively.

However, yes, you can build a custom kernel to eke out some performance
improvements.

Re: What processor features does Guix support on i686?

[Joshua Branson]

Leo Famulari <leo@famulari.name> writes:

> On Sun, May 02, 2021 at 12:56:45PM -0400, Joshua Branson wrote:
>> I'm kind of curious, if I were to compile my own linux kernel, and I
>> could someone select a newer processor family, would that make my kernel
>> a little more faster?  Or would it just make my kernel image a little
>> smaller?  Also my laptop is a Lenovo T400.    So it doesn't exactly have
>> NEW features.  :)
>
> Just to clarify, these kernel configuration options are for when one
> builds the kernel for "i686-linux" (Guix parlance) or "i386" (Linux
> parlance). This means 32-bit Intel-compatible.
>
> The T400 has a Core 2 Duo 64-bit procesor, so these options won't apply
> for you. That's "x86_64-linux" or "amd64", respectively.
>
> However, yes, you can build a custom kernel to eke out some performance
> improvements.

Thanks for the response!  I'm not quite so interested in building a
custom kernel yet.  But I think it would be cool to do one day!


-- 
Joshua Branson (joshuaBPMan in #guix)
Sent from Emacs and Gnus
  https://gnucode.me
  https://video.hardlimit.com/accounts/joshua_branson/video-channels
  https://propernaming.org
  "You can have whatever you want, as long as you help
enough other people get what they want." - Zig Ziglar