#### Back to index | # Info for ti99_4ev

#### Texas Instruments TI-99/4a Home Computer with SNUG EVPC video card

See the TI99/4a driver for non-EVPC information.

Known Issues:
EVPC emulation is not complete. The palette chip is not emulated.
The computer may crash on soft reset, though I have no idea why.

History and Trivia:
A common hack on the ti99/4a is replacing the old tms9918/9928/9929a with
an improved, upward-compatible v9938. This enhanced vdp supports true 16-
and 256-color graphic modes, high-res 512*192 graphic and 80-column text
modes, accelerated 2D graphics, etc. The only drawback is that some programs
(including TI's own TI BASIC) will not run with the v9938. Also, only
specially designed programs can take advantage of the improved graphic modes.
The EVPC card does just that: it includes a v9938 with 128kb of VRAM, 64kb of
extended RAM, an additional palette chip to program the palette in 256-color
mode, and a DSR ROM with various useful subroutines.
Also, this driver uses a hacked TI BASIC GROM so that TI BASIC will work
normally with the v9938. Only two bytes were modified to derive file
"994agr38.bin" from file "994agrom.bin": the bytes >F0 >0C >F8 at offset >216C
of the file were changed to >00 >0C >00. (This fix was contributed by Tony
Knerr, but I have no idea who invented it first.)

created on Mon May 19 14:44:27 2003