Re: That horrible hack from hell called A20

H. Peter Anvin
2000-12-06T18:57:59Z

"Richard B. Johnson" wrote:
>
> The protected-mode switch in INT 15 is probably the least tested BIOS
> function ever. I wouldn't trust it, and relying on it will put further
> burden on embedded Linux developers, many of whom don't even have a
> BIOS. It is 'least tested' because there is no way provided to get
> back to real-mode. This implies that somebody probably 'tested' it
> once, verified that some simple 32-bit function executed for a
> few microseconds, then declared; "It works!".
>

And of course, that's pretty much all we'd trust it to do. Personally,
I'd rather try to use the A20 gate function, if it works. I suspect that
between the machines where the BIOS or the KBC works, we should be close
to 100% coverage.

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."