Date: Tue, 24 Feb 1998 15:26:54 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Mike Smith <mike@smith.net.au> Cc: (Andrzej Bialecki) <abial@nask.pl>, yokota@zodiac.mech.utsunomiya-u.ac.jp, freebsd-current@FreeBSD.ORG, =?us-ascii?Q?S=F8ren?= Schmidt <sos@FreeBSD.ORG> Subject: Re: Proposed addition to panic() behaviour Message-ID: <XFMail.980224152654.shimon@simon-shapiro.org> In-Reply-To: <199802242125.NAA16540@dingo.cdrom.com>
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On 24-Feb-98 Mike Smith wrote: >> >> On 24-Feb-98 Søren Schmidt wrote: >> >> .... >> >> > It will only work on a std VGA card in a std mode. All moderne video >> > cards >> > demands specific programming (or what do you think the thousands of >> > lines >> > of code in Xfree86 does :) ) >> > >> > So your answer is it will not work most of the time, if at all. >> >> My ignorance shows all the time. When the system boots, something does >> something to the video card to make it go into a sane VGA mode. My >> ignorant assumption is that this something can be emulated/repeated with >> software in kernel mode. > > That something is card-specific code in the BIOS ROM on the card. You > may see it signing on if your monitor warms up quickly enough. > > This is real-mode 8086 code which can make all sorts of assumptions > about the state of the machine at that point in the boot phase. Some > of those assumptions aren't valid when the kernel is running. (Some > are, but to get to a mode where you can run this code is a bit > daunting.) These entry points are known and standardized. since we are talking panic mode here, switching back to realmode, to reset the video card to standard VGA mode can be considrered and will have a very positive support impact. Simon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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