Below is video showing how much faster this system runs Parsec when compared to the original TI-99/4A. And indeed that it does run Parsec - it is the first graphics mode 2 application I tried on the hardware. It just runs the game too bloody fast, fuel is consumes very fast and one can forget about refuelling the ship, the tunnels just fly by.

As quick recap, the system already supported quite lot of features:

• TMS99105 CPU running at 20MHz (200 ns machine cycle time)
• Memory initialisation from PC over USB
• Keyboard support from PC over USB, with PC app to forward keypresses
• 8K ROM (stored in RAM) at address 0
• GROM system, supporting up to 64Kbytes of GROM content. The system GROMs occupy 24Kbytes (18K of that used).
• RAM memory
  • Scratchpad of 256 bytes - actually 1K in this system
  • RAM expansion 32K bytes
  • Further RAM mapped to I/O extension ROM area 4000..5FFF
• Paged cartridge ROM emulation (8K pages, 8 pages supported, i.e. 64Kbytes maximum cartridge size)
• TMS9918 Video processor emulation
  • Graphics mode 1
  • Sprites - my implementation only supports 16x16 pixel sized sprites. It does not suffer from the limitation of only having 4 visible sprites per scanline. Now that I am writing this I have not actually tested this...

But these were not enough to run Parsec. That game required support of graphics mode 2. Luckily that part very easy, before adding support for that I did not realise I was only two if-then-else VHDL statements away from that. While at that, I fixed a few bugs related to the sprite hardware.

With that the new features are:

• Support for VDP graphics mode 2
• Improved support, i.e. less bugs, in sprite handling at screen edges