Re: Black box flight recorder for Linux

Krzysztof Halasa
2006-04-10T19:44:10Z

"linux-os \(Dick Johnson\)" <linux-os@analogic.com> writes:

> Further, in a boot where the BIOS needs to initialize hardware,
> It will write all RAM before enabling NMI. This makes sure that
> the parity bit(s) are set properly. Most BIOS will attempt to
> preserve RAM on a 'warm' boot as a throw-back to the '286 days
> with their above-1MB-memory-manager paged RAM because the
> only way to get back from protected mode to 16-bit real mode
> was a hardware reset.

I think there is no distinction WRT RAM test between cold and warm
boot anymore. If the BIOS clears the RAM is, I think, determined by
the "fast POST" option in BIOS setup (it always checks the size
so some bytes will be changed anyway).

> When using a memory-manager like DOS's
> HIMEM.SYS, you might actually be rebooting the machine hundreds
> of times per second!

Yes but it uses (or, rather, used) a CMOS flag to skip POST (not only
the RAM test) and to go directly to the entry point in real mode.

IIRC (I may be wrong, that was 15+ years ago) only 286 required
KBC reset to return to real mode (did LOADALL matter?), 386s have
no such problem.

BTW I understand the idea have nothing to do with actual aircraft,
so it would be the admin rather than NTSB looking at the data(?).
--
Krzysztof Halasa