hermit@shockeye.UUCP (Mark Buda) (12/14/88)
I recently downloaded a file from a local bulletin board (interrup.arc on simtel20) that is chock full of wonderful information on assorted interrupts. Imagine my puzzlement when I read (under the BIOS set video mode int) that my Paradise VGA Plus board has a 640x480 256-color mode! I looked in the little booklet you get with the board, and there's not mention of it. It's not advertised anywhere I've seen either. So I played with it. 640 x 480 x 256 > 128K. Problem. How do you get access to the bottom half of the screen in this mode? I fiddled with the mysterious "Paradise Registers" and discovered that by putting 0x70 (I think) in Paradise register #2, I could write to the bottom of the screen BUT it also crashed the machine. If I disable interrupts, it doesn't crash the machine. Why do I have to disable interrupts to do this? What is the REAL magic procedure I need to get at the second 128K of video RAM? Inquiring minds want to know. -- Mark Buda / Smart UUCP: hermit@shockeye.uucp / Phone(work):(717)299-5189 Dumb UUCP: ...rutgers!bpa!vu-vlsi!devon!shockeye!hermit I hate this $%$@%!$@%!@$%@#$@!% machine. "A little suction does wonders." - Gary Collins
malloy@nprdc.arpa (Sean Malloy) (12/15/88)
In article <247@shockeye.UUCP> hermit@shockeye.UUCP (Mark Buda) writes: > Imagine my puzzlement when I read (under the BIOS set video >mode int) that my Paradise VGA Plus board has a 640x480 256-color mode! >I looked in the little booklet you get with the board, and there's not >mention of it. It's not advertised anywhere I've seen either. So I played >with it. 640 x 480 x 256 > 128K. Problem. How do you get access to the >bottom half of the screen in this mode? >Why do I have to disable interrupts to do this? What is the REAL magic >procedure I need to get at the second 128K of video RAM? Inquiring minds >want to know. I don't want to rain on your parade, but 640x480x256 on a VGA board requires 44K _more_ memory than a 256K VGA board has, so you won't be able to use that mode unless you've got 512K on your VGA board (it actually requires 300K). The reason that you're crashing your system is that you're trying to write into nonexistent memory on your graphics board. If you still want to play with higher-resolution modes on a VGA, all the resolutions are set the same way that the MODE command does it -- 320x200x256 is mode 0x13, for example. The file VGIF36.ARC in PD1:<MSDOS.GIF> on SIMTEL20 has, in the documentation, a list of some of the extended VGA modes available on various boards, and the mode numbers that is 'standard' for them. The VGIF program itself will display the modes that your board will handle at the top of the screen above the GIF file list when run, as well. Sean Malloy Navy Personnel Research & Development Center San Diego, CA 92152-6800 malloy@nprdc.arpa
liber@darth.UUCP (Eric Liber) (12/16/88)
> interrupts. Imagine my puzzlement when I read (under the BIOS set video > mode int) that my Paradise VGA Plus board has a 640x480 256-color mode! > I looked in the little booklet you get with the board, and there's not > mention of it. It's not advertised anywhere I've seen either. So I played > with it. 640 x 480 x 256 > 128K. Problem. How do you get access to the ^^^^^^^^^^^^^^^ I have the Paradise VGA 16 plus and i didn't know about this either but... Let's think about this for a minute. These boards (8 and 16) come with 256k of ram on board. To get 256 colors requires 8 bits (a byte). If we multiply the pixel counts 640 x 480 = 307200 (or 300K). It looks to me like we are short 56k from filling the screen. If you devide 256K (262144) by 640 lines we can get 409 lines with 256 colors. And lo and behold there is indeed a supported resolution of 640 x 400 x 256! What I think is happening here is that Paradise also makes a VGA professional board that does have a 640 x 480 x 256 color resolution. (Actually it will go to 800 x 600 x 256 ). ( 800 x 600 = 480000 bytes necessary). While looking at the board (VGA 16 plus) i noticed an unused ram row and position for one support chip on the board... Is it just possible that the professional board is just the VGA 16 plus with more ram? If so It would make sense that the BIOS would probably be the same for all of the boards. Any paradise people out there to verify or deny this? Before you flame paradise for holding out on us this is very common in the electonic hardware arena. Make one board and firmware and simply do or do not include some chips to provide the level of price/performance you want. It makes a lot of sense from a marketing and production standpoint. good luck .. Eric (the red) Liber
hermit@shockeye.UUCP (Mark Buda) (12/17/88)
In article <1180@skinner.nprdc.arpa> malloy@nprdc.arpa (Sean Malloy) writes: >In article <247@shockeye.UUCP> I ask: >> [How do I write to the bottom of half of a Paradise VGA board in >> undocumented video modes?] > >I don't want to rain on your parade, but 640x480x256 on a VGA board >requires 44K _more_ memory than a 256K VGA board has, so you won't be >able to use that mode unless you've got 512K on your VGA board (it >actually requires 300K). Oh. I hadn't bothered to think of that. Nevertheless, I get the same problem with 640x400x256 mode, which requires less than 256k. >The reason that you're crashing your system >is that you're trying to write into nonexistent memory on your >graphics board. No that's not it, because the same problem happens in 640x400x256 mode. Anyway, why would disabling interrupts keep it from crashing in that case? The board has 256K. I know how to put it into 640x400x256 mode. I _can_ write to the bottom half of the screen. I want to know if there is a 'right' way to do it, that doesn't involve having to disable interrupts. -- Mark Buda / Smart UUCP: hermit@shockeye.uucp / Phone(work):(717)299-5189 Dumb UUCP: ...rutgers!bpa!vu-vlsi!devon!shockeye!hermit I hate this $%$@%!$@%!@$%@#$@!% machine. "A little suction does wonders." - Gary Collins
network@hgcvax.uucp (craig chaiken) (12/18/88)
> I have the Paradise VGA 16 plus and i didn't know about this either but... > Let's think about this for a minute. These boards (8 and 16) come with > 256k of ram on board. To get 256 colors requires 8 bits (a byte). > If we multiply the pixel counts 640 x 480 = 307200 (or 300K). It looks to me > like we are short 56k from filling the screen. If you devide 256K (262144) > by 640 lines we can get 409 lines with 256 colors. And lo and behold there I wrote an assembly language routine which allows me to address 640x409x256 colors on my Paradise VGA Plus. While the display is beautiful once the drawing is done, it suffers from terrible snow effects whenever the display is updated. In others words, the quality is unacceptable. I imagine THAT is the reason Paradise chose not to document it. In any case, I can post my routine if anyone is willing to trade quality for resolution. Craig Chaiken Hartford Graduate Center Computing Services
liber@darth.UUCP (Eric Liber) (12/20/88)
Yes I would like to see your code. I am always interested in how someone else does these things. Thanks for the Offer. Eric (the red) Liber
manuel@hpspkla.HP.COM (John L. Manuel) (12/22/88)
YES!,
Please post your 640x480x256 program example! I have been trying to
get documentation on how to get to these modes and have been unsuccessful
so far. I would really like to see this.
Thank-you
John Manuel
manuel@hpspkla.HP.COMnetwork@hgcvax.uucp (craig chaiken) (12/23/88)
accessing the undocumented 640x409x256 color mode on the
Paradise VGA Plus card, so I am posting the code. This is
Turbo Pascal 4.0 (or higher) source which displays a preprocessed
TARGA-16 file (512x400x32768 colors). The program expects the first
768 bytes of the file to define 256 palette entries. It expects 400
records of 512 bytes each to define the contents of the 400 pixel rows.
The pixel rows start at the bottom, rather than the top of the display.
I would post the program used to reduce the 32768 TARGA-16 colors to
256 VGA colors, but I just got a nice letter from Kenneth Sheldon of
BYTE, and its seems that they would like to see my article of the
subject. If BYTE decides not to publish it, I will certainly share it
here.
Craig Chaiken
Hartford Graduate Center
Computing Services
------------------------------ CUT HERE --------------------------
program raster_to_super_vga;
(*************************************************************
* 640x400x256 Color Raster to VGA Mode 5EH (RAS2SVGA.PAS)*
* by Craig Chaiken *
* September 24, 1988 *
*************************************************************)
uses dos;
var i,j:integer;
regs:registers;
infilevar:file;
buf:array[0..767] of byte;
numread,segment,offset:word;
begin
regs.ax:=$5e; (*** Video Mode 5EH, 640x400x256 Colors ***)
intr($10,regs);
(*** Load Color Raster File into Memory Buffer ***)
assign(infilevar,paramstr(1));
reset(infilevar,1);
blockread(infilevar,buf,768,numread);
(*** Initialize Palette from First 768 Bytes of File ***)
regs.ax:=$1012;
regs.bx:=$0;
regs.cx:=$100;
regs.es:=seg(buf);
regs.dx:=ofs(buf);
intr($10,regs);
(*** Display Image to Screen ***)
for j:=399 downto 0 do
begin
segment:=$a000+((j mod 96)*$28);
offset:=15*(j div 96);
port[$3ce]:=$9;port[$3cf]:=offset;
blockread(infilevar,mem[segment:0],512);
end;
close(infilevar);
(*** Exit and Restore to Text Mode Upon Sensing Carriage Return ***)
readln;
regs.ax:=$3;
intr($10,regs);
end.