#543 Limit TMS VDP VRAM access

Manuel Bilderbeek — Sun, 14 Sep 2014 20:30:01 -0000

Mostly implemented in commit ddcd3a47a22375a1266a405bf23c6c7b8c0de457 by Wouter (thanks!). But it is not exactly known/sure yet what the value for the delta is on the TMS, see VDP.cc:

// TODO how many extra cycles on TMS99x8?
//  To be on the save side, I picked 10 cycles, translated to
//  V99x8 that's x4 = 40cycles.
// See doc/internal/vdp-vram-timing/vdp-timing-2.html for details.

If I understand correctly, Wouter wants to keep this ticket open until the definitive value is determined (how?).

Limit TMS VDP VRAM access

Laurens Holst — Wed, 23 Jul 2014 17:08:46 -0000

Currently, the limits on accessing the VRAM of the various TMS VDPs are not emulated.

The VRAM access timing is very accurately described in section 2.1.5 of the application manual:

http://map.grauw.nl/resources/video/texasinstruments_tms9918.pdf

Also there are some interesting tidbits of the inner workings of the TMS VDP range in these records of an interview with one of its designers Karl Guttag: http://spatula-city.org/~im14u2c/vdp-99xx/

Recent changes to 543: Limit TMS VDP VRAM access

#543 Limit TMS VDP VRAM access

Limit TMS VDP VRAM access