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page flipping 13h

Fri, 11 Jan 2002 10:31:11 -0700

Is there a way to do page flipping in 13h mode? With ASM or something? Also, where are the "pages" located (address), so I can draw on them.
And, if that's not possible, is there a "fast" way to swap a 64000 byte array from RAM to the position of videoram?
So far all I know is copying it byte for byte and that's awfully slow.

Re: page flipping 13h

Sat, 12 Jan 2002 17:31:09 -0700

: Is there a way to do page flipping in 13h mode? With ASM or something? Also, where are the "pages" located (address), so I can draw on them.
: And, if that's not possible, is there a "fast" way to swap a 64000 byte array from RAM to the position of videoram?
: So far all I know is copying it byte for byte and that's awfully slow.
:

Hmmm...
There is practicly no graphic card out there with less
than 256kb ram on it. Actually standard is pretty much
32 or 64MB. So if you like to do some research on
graphic controller(s) you will find that you can create
different modes (even your own) by altering VGA registers.
You could have up to 4 pages without major effort (Xmode, etc.).
If all you want is fast copy routine to dump something
from RAM to video memory, try this:

http://www.programmersheaven.com/msgboard/read.asp?Board=16&MsgID=50882& Setting=A9999F0001

(Note: Check the dump2screen )

It uses 32-bit to transfer 4 bytes (pixels) at a time.

Iby

Re: page flipping 13h

Wed, 14 Aug 2002 18:31:51 -0700

: Is there a way to do page flipping in 13h mode? With ASM or something? Also, where are the "pages" located (address), so I can draw on them.
: And, if that's not possible, is there a "fast" way to swap a 64000 byte array from RAM to the position of videoram?
: So far all I know is copying it byte for byte and that's awfully slow.
:

what i usually do is make a 64k heap variable and treat it as a virtual screen

and here's a 16 bit proc that moves bytes from source to dest quite fast:(actually it moves words and not bytes so make sure your virtual screen's size or whatever is a multiply of 2 - 64000 is just fine)

procedure MoveW(var source,dest;count:word);assembler;
asm
MOV AX,DS
LES DI,dest
LDS SI,source
MOV CX,count
CLD
REP MOVSW
MOV DS,AX
end;

here's how you copy thhe virtual screen to the active page:

MoveW(VScreen,mem[$a000:$0000],64000);

if you had hardware page flipping in mind i cant help you
hm
hope i helped you :)

Re: page flipping 13h

Wed, 14 Aug 2002 23:26:05 -0700

: : Is there a way to do page flipping in 13h mode? With ASM or something? Also, where are the "pages" located (address), so I can draw on them.
: : And, if that's not possible, is there a "fast" way to swap a 64000 byte array from RAM to the position of videoram?
: : So far all I know is copying it byte for byte and that's awfully slow.
: :
:
: what i usually do is make a 64k heap variable and treat it as a virtual screen
:
: and here's a 16 bit proc that moves bytes from source to dest quite fast:(actually it moves words and not bytes so make sure your virtual screen's size or whatever is a multiply of 2 - 64000 is just fine)
:
: procedure MoveW(var source,dest;count:word);assembler;
: asm
: MOV AX,DS
: LES DI,dest
: LDS SI,source
: MOV CX,count
: CLD
: REP MOVSW
: MOV DS,AX
: end;
:
:
: here's how you copy thhe virtual screen to the active page:
:
: MoveW(VScreen,mem[$a000:$0000],64000);
:
: if you had hardware page flipping in mind i cant help you
: hm
: hope i helped you :)
:

Two more issues:

VGA memory always starts at $A000. What I did most of the time when I was using Mode13, is to define a global array which is set to that address:

var VIDEO : array[0..63999] of Byte absolute $A000:$0;

even easier:

var VIDEO : array[0..199,0..319] of Byte absolute $A000:$0;

Note that it's [y,x], not the other way around!

Hardware flipping is possible by changing the graphics adapters "start address" register, you can also easily make vertical scrolling with that. Sorry - don't know the code, can not remember it because it's so long ago since I used this the last time and unfortunately I don't have it handy ... it's about 10,000 miles away from where I am right now

Check the standard VGA registers, you will find it. I remember that it's very easy (just 2 or 3 port[...] statements).

Hope that helped somehow.

tron.

Re: page flipping 13h

Thu, 15 Aug 2002 02:37:34 -0700

correction:

in my previous reply i wrote:
MoveW(source,dest,64000);

make it:
MoveW(source,dest,32000);
because it copies words and not bytes