17 Jul
2008
17 Jul
'08
9:44 a.m.
> Actually, I wrote some 6502 asm to bit bang out
the game port
> data, ttl rs232 ;-) . It isn't that hard.
Did that to move Infocom game sectors from an Apple II
to a C-64.
It was a bit rough, but with both CPUs bit-banging away at 1200
baud, it took a while. In the end, though, the operation was a success.
Likewise, once did a similar thing to transfer a particularly interesting textual
adventure game from an Apple II to an Atari 800. Cobbled together a three-wire cable
between game ports on each machine and used a very simplistic transfer method: Used one
conductor as a single-bit DATA line, another for RCVR-READY, the last for signal ground.
We sent just one bit at a time, with the RCVR-READY basically ACKing each bit. Certainly
wasn't an efficient way to send data, but there was no reason to finesse it any more,
since it was a one-time setup.
If I remember right, we figured that our 42KB transfer would take about 75 minutes. After
a slightly extended lunch, the transfer was complete. I guess that works out to about 10
bytes per second! With a few more minutes to patch the 'TTY-IN' and
'TTY-OUT' entry points, we had a fully working app. If I remember correctly, we
even figured out how to modify the game save functionality for the Atari, too.
- Jared