🚀 go-pugleaf

I downloaded the TRI32NEW.ZIP package and tried to install the
800x600x256 driver on my 512K VGA-Wonder board.  As everyone else
reported, the top 88 lines were duplicated on the bottom of the
screen, and vice versa.  AFter spending much time with a friend going
over the SVGADATA.PMI file, we found a bug in it: CRT register 9 was a
0, causing the Line Compare Register to contain 511 - causing a split
screen at row 512, exactly what happened.  According to my specs, bit
6 of the Maximum Scan Line register (R9) should be set to a 1, to
yield a Line Compare value of 1023 - below the bottom of the screen.

Unfortunately, changing the value of this in the SVGADATA.PMI file did
nothing.  As a matter of fact, nothing happened after chaning ANY of
the normal IBM regusters (sequencer, CRT, GDC, and attributes).  The
only registers that had any effect were the ATI-specific ones (at
1ce/1cf on my system), and they only made things worse.

Since Joel Armengaud's ATI256C2 driver uses the SVGADATA.PMI file
without this bug, I assumed that the BVHSVGA.DLL file is ignoring the
IBM-standard register listings in the SVGADATA.PMI file, and is only
reading the manufacturer-specific portions - leaving the device driver
to itself when setting the registers.

Anyway, does this seem to make sense?  Is there anything I can do
about it, short of getting source code to the driver?  Interestingly
enough, other chipsets (like TSENG) correctly set the Line Compare
register to 1023, so the Trident drivers don't have this problems on
those systems.

I tried searching through the SVGA600.DLL file for a parameter table
to patch, but this is nearly impossible.  I ran EXEHDR on the .DLL,
but IBM hasn't documented the output (for 32-bit DLL's) completely
enough, so I can't locate any of the "prime-candidate" modules in the
.DLL file to look at them.
-- 
  |)  David Charlap          | .signature confiscated by FBI due to
 /|_  dic5340@hertz.njit.edu | an ongoing investigation into the
((|,)                        | source of these .signature virusses
 ~|~