Miod VallatMar 5

Good morning! Today, the last part of the #OpenBSD/sgi story is available.

In this episode, hardware conditions documented as "Can't happen" happen, and support for one particular CPU model "everyone agrees will never get supported by free software" gets nevertheless written.

Read it at:
http://miod.online.fr/software/openbsd/stories/sgi6.html

You can also now read the whole story in one page:
http://miod.online.fr/software/openbsd/stories/sgiall.html

I'll return to the usual "new material on wednesdays" schedule next week.

OpenBSD on SGI, 6/6: The last challenges

Show threadTodd KnarrMar 6
@miodvallat "Can't happen" is inevitably a false statement. In software, if it really "couldn't happen", the compiler would be complaining about unreachable code. If it isn't, it's not "can't happen" but rather "must not be allowed to happen".
Show threadmirabilosMar 6
@tknarr @miodvallat this is a hardware thing tho
Show threadTodd Knarr

@mirabilos @miodvallat Same principle. If it really couldn't happen, your design software would've optimized those gates out of existence because they don't affect the outputs.

Related to the switch labelled "magic" and "more magic" and a note "do not change switch position".

Mar 6 at 2:36amWeb
Show threadmirabilosMar 6

@miodvallat @tknarr that’s… a very naïve worldview.

and a very mid-2020s worldview that does not apply to 1990s hardware

Show threadMiod VallatMar 6
@tknarr @mirabilos Well, the fact that the hardware had the ability to report this condition obviously hints it can happen. But documentation writers can be abused and write too confident sentencies 😋