From: zmbenhal@netcom.com (Zeyd M. Ben-Halim) Subject: Re: How to switch back to VGA-text from SVGA-text mode??? Date: 29 Mar 1993 22:39:40 GMT
In article <1993Mar29.205002.20670@primerd.prime.com> cummings@hammer.prime.com (Kevin Cummings) writes:
>> Sorry, I don't understand. The basic interface of the cards MUST be
>> the same at some level, or the common BIOS couldn't talk to all of them.
>> Why can't a Linux program be written that, in effect, acts as the BIOS
>> does? I can see that it might have to execute in real mode, which might
>> be a problem. Other than that, what is so magic about the BIOS?
>
>It's a "system call" under DOS, but not under LINUX. The code you need to
>execute is in the EPROM on your video card, but its been setup for a memory
>model that LINUX does not support. Therefore it is useless to LINUX.
>(Well, not entirely, I suppose that you could execute it through a VM86
>task, but that would require a lot of kernel work, and trap code to catch
>and deal with the IO to the video registers. At least that's the way it
^^^^^^^^^^^^^^^^^^^^^^^^^
This is pretty easy and is alreadyy done (otherwise you couldn't have any
graphics programs) The difficulty is finding out the values that go in which
register for each card. The BIOS code (for mode switching) has to run in real-
mode.
>was explained to me a year ago when the question first came up.)
>
>--
>Kevin J. Cummings ComputerVision Services
>cummings@kjc386.framingham.ma.us cummings@primerd.Prime.COM