Message-Id:	<199707032125.VAA32469@mx2.rmplc.co.uk>
From:	"Liam" <marl AT rmplc DOT co DOT uk>
To:	<djgpp AT delorie DOT com>
Subject:	Re: [Q] Inline Assembly
Date:	Thu, 3 Jul 1997 22:17:53 +0100
MIME-Version:	1.0

Eric Jacobs <no AT no DOT no> wrote:
> To: djgpp AT delorie DOT com
> Subject: Re: [Q] Inline Assembly
> Date: 30 June 1997 13:40
> 
> John Eccleston wrote:
> > 
> > Hi All,
> > 
> > I am having little difficulty trying to copy my double buffer to
> > video memory and I was just wondering if anyone could put me out of my
> > misery and tell me why the following code gives me a striping effect on
> > the screen.
> > 
> > -----> Cut here <-----
> > void vgaBlitBuffer(BYTE *buffer)
> > {
> >    int
> >       selector = _dos_ds;
> > 
> >    /* Synchronise with vertical retrace to avoid flicker */
> >    while ((inportb(IST1_ADDR) & 0x08) == 0); /* Wait for vertical
retrace */
> >    while ((inportb(IST1_ADDR) & 0x08) == 8); /* Wait for end of retrace
*/
> > 
> > #if 0
> >    /* Blit the double buffer */
> >    movedata(_my_ds(), (int) buffer, _dos_ds, 0xA0000, 320 * 200);
> > #else
> >    asm("movw %%ax, %%es\n\t"
> >        "movl $0xA0000, %%edi\n\t"
> >        "movl $16000, %%ecx\n\t"
> >        "cld\n\t"
> >        "rep\n\t"
> >        "movsl\n\t"
> >        : /* no output registers */
> >        : "a" (selector), "S" (buffer)
> >        : "%eax", "%esi", "%edi", "%ecx");
> > #endif
> > }
> 
> Your mov's are backwards! It's   mov dest,src
No there not, it uses AT&T synatx which is
	mov	src, dest


> 
> Also, I believe there is an inline function in movedata.h called
_movedatal
> that is exactly what you want here. You call it the same way as movedata
> except you specify 16000 (longs) as the count instead of 64000 (bytes).
> 
> -ej
Liam

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