🚀 go-pugleaf

In article: <817836376snz@grove.demon.co.uk>  "Donald R. Oddy" 
<donald@grove.demon.co.uk> writes:
> 
> In article <816978470snz@siberia.demon.co.uk>
>            philip@siberia.demon.co.uk "Philip McNab" writes:
> 

> >b) the BIOS functions/memory addresses that I could use to determine
> >   this?  I'm a reasonably skilled C programmer, with Turbo C v2.

You need to use function 1B if it's a VGA card. Function 4F, subfunction 00, if 
it's an SVGA card. These functions will return more info on the card than you'll 
ever want to know.

The following table is for function 1B (VGA) :

Register	Call Value	Return Value
AH		1B
AL				1B
BX		0
DI		buffer offset	*
ES		buffer segment	*

* = buffer contents

Offset		Size		Contents
00		dword		address of table with BIOS function capabilities
04		byte		video mode
05		word		number of displayed character columns
07		word		length of displayed range of video RAM
09		word		start address of upper left column on monitor
0B		16 bytes	8 cursor positions for 8 screen pages
1B		byte		cursor end
1C		byte		cursor start
1D		byte		number of active screen page
1E		word		I/O address of CRTC address register
20		byte		value of mode select register
21		byte		value of palette register
22		byte		number of displayed character lines
23		word		height of displayed matrix in scan lines
25		byte		code for active video combination
26		byte		code for inactive video combination
27		word		number of simultaneously displayed colours
29		byte		maximum number of screen pages
2A		byte		number of scan lines (see below)
2B		byte		character table if attribute bit 3 = 0
2C		byte		character table if attribute bit 3 = 1
2D		byte		general status information
2E-30		3 bytes		reserved
31		byte		size of video RAM (see below)
32		byte		save status

No of scan lines : 0=200, 1=350, 2=400, 3=480
Size of video RAM : 0=64kB, 1=128kB, 2=192kB, 3=256kB

It's thankfully a lot simpler with SVGA (function 4f,00) :

Register	Call Value	Return Value
AH		4F		Status (00=OK, 01=Error)
AL		00		4F (if supported)
ES		segment of info buffer
DI		offset of info buffer

Offset		Size		Content
00		4 bytes		"VESA"
04		word		version
06		dword		far pointer to manufacturer's name
0A		4 bytes		implemented functions
0E		dword		far pointer to list of supported VESA modes and
				manufacturer's video modes
12		238 bytes	reserved

Notes on SVGA BIOS functions (4F) :

a) The functions listed are located in the BIOS extension of SVGA adaptors.
b) The SVGA BIOS moves the entry point for the INT10 handler of the system BIOS 
on the motherboard to INT42 upon booting.
c) The additional SVGA BIOS functions are accessed as subfunctions of 4F.


You *did* say that you were a reasonably skilled programmer. Have fun :)


-- 
John Naismith