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Using Multiple CPU Cores in DOS? (Miscellaneous)

posted by tom Homepage, Germany (West), 19.09.2011, 22:00

> I don't think I want that to be the default behavior, though, since it
> makes things INCREDIBLY slow
wrong. A20 will be enabled almost always, and only a few microseconds after program has started; you won't notice a difference

> -- too slow to depend on in an IRQ handler if
> there's a way to avoid it. I think my default is going to be to to enable
> A20 and leave it on
 changing system state at some randowm interrupt time might be one of the worst ideas in operating system design ever - even worse then 'my driver needs a second core'

> but have a user-selectable option to do it "the slow
> way".
have a user selectable option to do it the fast way

> Like you, I don't see a lot of point in making that the default
> behavior given the limited number of programs affected and the availability
> of LOADFIX.
 there's a tiny difference.

with these old programs, without LOADFIX, they would print a predictable error message, and exit.

now randomly enabling A20 at some randowm interrupt time removes the predictability (of failure), and instead introduces the feature 'works most of the time'

> I still think the possibility of using a second core to make the mode
> switches faster may still be worth investigating, though.
 as said above, mode switches are a few hundred thousands per second.

> Even when you
> don't have to mess with the A20 line, the mode switches are still
> noticeably slow when you need to do a lot of them in the background.
do you really need an entire core for this USB driver ?
one core exactly and only for your driver ?
or do you intend to run a real operating system on the second core, with
an API how multiple drivers can share this core, how they synchronize with the real mode part, ...

I don't expect to see this implemented this century ;)

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