Subject: Re: PCVT/virtual consoles
To: Chris G Demetriou <Chris_G_Demetriou@LAGAVULIN.PDL.CS.CMU.EDU>
From: David Brownlee <>
List: current-users
Date: 05/08/1995 16:42:11
On Mon, 8 May 1995, Chris G Demetriou wrote:

> In particular, if a driver can exploit certain hardware features on a
> given architecture, that otherwise wouldn't be exploited and that
> don't exist on other architectures... well, that's why drivers exist.
> For instance, it should be easy and very fast to provide a text-only
> virtual terminal emulation on PC's, because of the fact that they've
> got a text mode built into their video cards...  That'd be a lot
> harder on something like a sparc, which doesn't have built-in text
> mode.
	I don't see that it would be much more harder to do it for any
	other arch, assuming it sits abouve the standard console driver.
	Presumable pcvt maintains 10 'screens' and switches them by writing
	the appropriate one to the video card.  Doing this for an ANSI
	terminal connected to a serial line shouldn't be much more 
	difficult - send a clear screen followed by the data. In fact as
	long as you know how to clear the screen you could put it on top
	of any screen driver. The PC has an advantage in that it can do the
	'clear screen & update' by just copying over a block of memory, but
	that is the only output part that needs to be architecture specific.

	As for input - determining what is a function key... now that might
	take more work to get it right for all (Ok most :) cases.

> I'm not sure that i have a comment one way or another, except that we
> shouldn't be providing _two_ "standard" console drivers on the i386...
> 8-)
	For those people on 4Mb machines who really want to trim the
	kernel?.. Then again those are the people most likely not to be
	running X & so needing virtual terminals (& 'screen' pages a 4Mb
	machine to hell if you try doig any work :)

	(I've trimmed Chris's reply - but hopefully not lost any meaning :)

			David (MIME)    (+44) 171 477 8186    abs@Monochrome 
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