From: Kevin D. Quitt (KQuitt@ieeinc.com)
Date: Fri 08 Jun 2001 - 19:39:30 IDT
Here's the working routine, after much tracking through the code:
void setPalette( uchar *pal )
{
if ( !pal )
return;
while ( !(inb( 0x3DA ) & 0x08)); /* Wait for vertical blanking */
port_out( 0x01, SEQ_I ); /* Beam off */
port_out( port_in( SEQ_D ) | 0x20, SEQ_D );
port_out( 0, PEL_IW ); /* Send the palette */
outsb( PEL_D, pal, 256 * 3 );
port_out( 0x01, SEQ_I ); /* Beam on */
port_out( port_in( SEQ_D ) & 0xDF, SEQ_D );
}
The beam is turned off because this processor is so slow that it requires
not only the retrace time, but several scan line times as well to write the
entire palette.
I would also like to point out what I consider to be a flaw in
vga_waitretrace: it doesn't return until AFTER vertical retrace is over.
Generally speaking, one waits for vertical retrace to start so that one can
paint the palette during the free beam-off period.
I suggest, therefore, that line 42 in vgamisc.c be elided.
I also recommend that the routines that set the palette be modified to
operate similarly to the above function as it's many times faster. The
current routines call __svgalib_delay() between writes, but with the
default O3 compilation, that function is empty and the compiler just
removes the code and calls to it.
--
_
Kevin D. Quitt KQuitt@ieeinc.com
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