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KS2012: Supporting old/oddball architectures, tool chains, and devices

KS2012: Supporting old/oddball architectures, tool chains, and devices

Posted Sep 6, 2012 22:25 UTC (Thu) by gb (subscriber, #58328)
Parent article: KS2012: Supporting old/oddball architectures, tool chains, and devices

Two things seem missing in this article.

First, there are emulators. It's significantly easier to emulate 386 than core2-due i guess, and probably faster. Presence of emulators also means that you have no need to search for old 386 hardware to test 386 support.

Second, Peter seem approach linux kernel like a fully commercial product, he has a 'effort' which may be 'put' into some 'direction' or 'wasted' doing something that do not push 'product' forward. In fact, Linux would be dead if idea behind it dies, idea that software development is interesting. It's usually interesting to run on some unusual hardware, to fix some crappy bug and not 'supporting' such platforms is linux would mean more 'we do not accept patches for this outdated XXX' than 'we spent so many time on supporting it'.

I hope linux would not replicate fate of gnome which in 2.0 branch started from 'removing unusual and rarely used features' and finished up with complete rewrite in new shiny way everybody loves.


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KS2012: Supporting old/oddball architectures, tool chains, and devices

Posted Sep 6, 2012 23:10 UTC (Thu) by dlang (subscriber, #313) [Link]

> Presence of emulators also means that you have no need to search for old 386 hardware to test 386 support.

This assumes that the emulator is perfect.

There are differences between different flavors of 386 chips that sometimes trip things up.

As a smoke test and emulator is Ok, but it doesn't replace all testing on real hardware.

KS2012: Supporting old/oddball architectures, tool chains, and devices

Posted Sep 10, 2012 18:02 UTC (Mon) by BenHutchings (subscriber, #37955) [Link]

Indeed. For a while there was a bug in the 'alternatives' code that would cause 386 and 486 processors to crash because it patched an instruction that was already fetched into the pipeline. (Later processors will flush the pipeline in this case. These differences in behaviour are documented, by the way.) I very much doubt that, say, QEMU simulates processor behaviour down to this level - that would tend to make it much slower.

KS2012: Supporting old/oddball architectures, tool chains, and devices

Posted Sep 7, 2012 20:55 UTC (Fri) by wtanksleyjr (subscriber, #74601) [Link]

The cost of supporting legacy platforms is NOT merely the time and money it takes to run a few tests on those platforms; rather, it's the inability to add new features because they impact a code path that can't be tested because it's only exercised on the legacy hardware.

KS2012: Supporting old/oddball architectures, tool chains, and devices

Posted Sep 25, 2012 6:26 UTC (Tue) by muwlgr (guest, #35359) [Link]

80386 did not have 'cmpxchg' instruction which only appeared in i486.
I am not sure it is possible to emulate its absence with native KVM/QEMU.


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