Re: Architecture baseline for Forky

Why not support power 8 beyond 2028? It is still a good system and supports n=
ewer little endian. Hopefully, you can reconsider and keep power 8 for as lo=
ng as power 9/10 regarding baseline support.

> On Oct 26, 2025, at 5:40=E2=80=AFAM, Bastian Blank <[email protected]> wrot=
e:
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> =EF=BB=BFHi
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> We never did a real discussion about architecture baselines before, but I t=
hink
> we should do that.  We also don't have any guidelines what we as Debian wa=
nt to
> actually support.  But given that we are a general purpose distribution, w=
e
> have to find a balance.
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> As a general guidance I would like to aim for a ten to 15 years support ra=
nge
> at release time.  The cutoff in respect to the expected 2027 release date o=
f
> Forky would therefor be 2012 to 2017.  More time is given for widely used
> architectures, less for more specialized ones.
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> Bastian
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> # Current architecture baseline
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> Only three architectures set an explicit baseline in gcc-12 (Bookworm) and=

> gcc-15 (Forky):
> * armhf: armv7-a+fp
> * i386: i686
> * s390: z196
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> All other architectures use the default values.
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> # Proposal for architecture baseline
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> ## amd64 (and i386)
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> * x86-64-v2: Supported since around 2008[^x86]. Used in RedHat 9[^redhat9x=
86].
> * x86-64-v3: Supported since around 2013-2015[^x86]. Used in RedHat
>  10[^redhat10].
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> I propose to use the x86-64-v2 baseline in Forky.  It gives us more then t=
he 15
> years and everyone else already switched to it or even a newer variant.
> Factoring in a possible LTS for Trixie, this means that x86-64-v1 will sto=
p
> being supported by Debian in 2030.
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> ## ppc64el
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> * POWER8: Launched in 2014[^power8].
> * POWER9: Launched in 2017[^power9]. Used in RedHat 9[^redhat9] and
>  10[^redhat10].
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> I propose to use the POWER9 baseline in Forky.  The Debian infrastructure s=
eems
> to be comprised of all POWER9s.  This means POWER8 will stop being support=
ed in
> 2028.
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> ## s390x
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> * z14: Launched in 2017[^z14]. Used by RedHat 10[^redhat10].
> * z15: Launched in 2019[^z15]. Used by next Ubuntu.
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> I propose to use the z15 baseline in Forky.  Yes, this is less then ten ye=
ars,
> but s390 is such a niche architecture and all we do is best (often not eve=
n
> this) effort support.  The Debian infrastructure is documented to be at le=
ast
> z15, all accesible system are actually z16.  This means that z14 and older=
 will
> stop being support in 2028.
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> # How to see supported baseline
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> The dynamic linker of glibc can show what microarchiture level it consider=
s
> supported on the current CPU.  The "supported" marker is relevant in this c=
ase.
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> ## amd64
> ```
> % /usr/lib64/ld-linux-x86-64.so.2 --help | sed -n '/^Subdirectories of gli=
bc-hwcaps/,$p'
> Subdirectories of glibc-hwcaps directories, in priority order:
>  x86-64-v4
>  x86-64-v3 (supported, searched)
>  x86-64-v2 (supported, searched)
> ```
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> ## ppc64el
> ```
> % /usr/lib64/ld64.so.2 --help | sed -n '/^Subdirectories of glibc-hwcaps/,=
$p'         =20
> Subdirectories of glibc-hwcaps directories, in priority order:
>  power10
>  power9 (supported, searched)
> ```
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> ## s390x
> ```
> % /usr/lib/ld64.so.1 --help | sed -n '/^Subdirectories of glibc-hwcaps/,/^=
  z15/p'          =20
> Subdirectories of glibc-hwcaps directories, in priority order:
>  z16 (supported, searched)
>  z15 (supported, searched)
> ```
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> [^power8]: https://en.wikipedia.org/wiki/POWER8
> [^power9]: https://en.wikipedia.org/wiki/POWER9
> [^x86]: https://en.wikipedia.org/wiki/X86-64#Microarchitecture_levels
> [^z14]: https://en.wikipedia.org/wiki/IBM_z14_(microprocessor)
> [^z15]: https://en.wikipedia.org/wiki/IBM_z15_(microprocessor)
> [^redhat9]: https://docs.redhat.com/en/documentation/red_hat_enterprise_li=
nux/9/html/9.0_release_notes/architectures
> [^redhat9x86]: https://developers.redhat.com/blog/2021/01/05/building-red-=
hat-enterprise-linux-9-for-the-x86-64-v2-microarchitecture-level
> [^redhat10]: https://docs.redhat.com/en/documentation/red_hat_enterprise_l=
inux/10/html/considerations_in_adopting_rhel_10/architectures
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> --
> Spock: The odds of surviving another attack are 13562190123 to 1, Captain.=

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