From the PC side, you can access on the MD side:
- All RAM
- All VDP registers (incl VRAM and CRAM)
- Yamaha OPN FM chip
- Ti PSG chip
- Z80 memory and registers
- Joystick ports
You cannot access the cartridge slot or the TMSS (lockout chip) ROM.
From the MD side, you can access on the PC side:
- All RAM
- All ROMs (e.g. system BIOS, VGA BIOS, and any option ROMs)
- All IO space (e.g. serial/parallel ports, VGA registers, interval
timer, any ISA cards not requiring DMA or interrupts like AdLib or POST analyser cards)
You cannot use BIOS routines, as the CPU is halted, so no DMA or
anything that relies on interrupts.
I'll need to watch the video sometime... Tomorrow maybe!
Let me know how you go!
As of right now, there are exactly *TWO* packages that make use of the TeraDrive's capabilities. Puzzle Construction Set, a demo included with the system showing off what can be done. And "The Manhole", an adventure game by Cyan (of MYST fame), published by Activision, which uses a
special driver to access the Yamaha OPN FM chip.
And I guess my demo makes three! :D
Unfortunately there is a specific setup routine needed to unlock the MD hardware from the PC side, and bespoke ways of accessing it, so you
can't use any old game with, say, AdLib support.
Hope this answers your questions!
That is really cool. I guess it makes sense that the PC CPU is halted - I did wonder about that. Was such an experimental time...
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