Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: backward architecture, The Design of Design
Date: Thu, 09 May 2024 13:39:55 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
Lines: 27
Message-ID: <2024May9.153955@mips.complang.tuwien.ac.at>
References: <v03uh5$gbd5$1@dont-email.me> <20240507115433.000049ce@yahoo.com> <v1fim7$3t28r$1@dont-email.me> <20240508141804.00005d47@yahoo.com> <v1gncp$1en9$1@gal.iecc.com> <20240509105422.0000333e@yahoo.com> <v1i0ur$i07r$1@dont-email.me> <20240509135356.000006c1@yahoo.com> <2024May9.141347@mips.complang.tuwien.ac.at>
Injection-Date: Thu, 09 May 2024 15:46:32 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="985c0fa2ceb1cd942b6918d37505d352";
	logging-data="700190"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18Nq5bXVY3LVJPw1f9s4c72"
Cancel-Lock: sha1:dzcuMWuD+t+6xqF1jlDpBIrFq7M=
X-newsreader: xrn 10.11
Bytes: 2353

anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>Michael S <already5chosen@yahoo.com> writes:
>>On Thu, 9 May 2024 08:19:39 -0000 (UTC)
>>> The term comes from Brooks.  Specifically, he applied it to the
>>> S/360 line of computers which had a very wide performance and
>>> price range, and programs (including operating systems) were
>>> binary compatible from the lowest to the highest performance and
>>> price machine.
>>
>>
>>I suppose, it means that my old home PC (Core-i5 3550) is downward
>>compatible with my old work PC (Core-i7 3770). And my old work PC is
>>upward compatible with my old home PC.
>
>Given that both use Ivy Bridge CPUs, there is no compatibility issue
>as far as the CPU is concerned.

Actually, there are cases where this is not true: Intel sabotages
upwards/downwards compatibility by disabling architectural features on
cheaper models (in particular, they disabled AVX on Ivy Bridge CPUs
sold as Pentium G or Celeron G).  But for your Core ix-based Ivy
Bridges, AFAIK there is no such problem.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>