From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lucio De Re <lucio@proxima.alt.za>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] delay and aamloop
Message-ID: <20020128075040.I9246@cackle.proxima.alt.za>
References: <20020127192032.87D9B19988@mail.cse.psu.edu>
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In-Reply-To: <20020127192032.87D9B19988@mail.cse.psu.edu>; from Russ Cox on Sun, Jan 27, 2002 at 02:20:30PM -0500
Date: Mon, 28 Jan 2002 07:50:40 +0200
Topicbox-Message-UUID: 4700c872-eaca-11e9-9e20-41e7f4b1d025

On Sun, Jan 27, 2002 at 02:20:30PM -0500, Russ Cox wrote:
>
> AAM is "ascii adjust AX after multiply", which may
> well have been on the 80186.  It fools with AX but
> that's about it.
>
Yes, I realised with further mucking about that the actual contents of
the delay() function has nothing to do with the problem and/or the
symptoms.

By looping 100000 times (10^5) instead of 10^4, I managed to stall the
entire loading process, where 10^3 seems to work fine for
boot/pc/9load but I haven't been able to try it on 9/pc/9pcdisk.gz,
for example.

Something is dependent on timing in the most intractable fashion.  I
have to confess that I do not like the PC startup code at all, not
Plan 9's nor anyone else's.  It looks like a whole lot of compromises
waiting to bite one.

And, sadly, once the hurdle is overcome things behave themselves very
nicely, so there's little reason to go back and apply a more pervasive
fix.

But I'm hoping to put some effort into a bootstrap procedure that is
more robust than we have now, even if I have to lift it from Linux or
NetBSD (or, most likely, the IBM PC/XT BIOS code from the
long-cherished Technical Reference Manual).

Thank you for confirming what I already suspected.

++L