Re: [stella] 6502 hardware register writes

[AutismUK@xxxxxxx]

In a message dated 03/11/01 22:01:09 GMT Standard Time, john@xxxxxxxxxxx writes:

In any case I wouldn't say Andrew has no chance of success.  Especially if
he has some clever new emulation architecture.  Besides, it shouldn't take
more than a couple of weeks to code up enough of an emulator to draw a
playfield and a couple of players.  From that one could see what the
performance will really be like before investing too much in the details.

The problem being that whereas with most emulators you spend most of
the time executing code, in a 2600 you spend most of it executing the
TIA.

A26 (the basis of Z26) used a scam whereby it checksummed the
data transfer and timing to the TIA and its current state, and if the
checksum didn't change the screen didn't either, worked better for
some games than others, of course, but got it running on the target
(my then 486SX2/50) and this worked to about a level of 95%; but
stuff like Freeway 2 player didn't work, let alone Cosmic Ark :)

It also used entirely the 8086 instruction set because it was coded
in A86, so it had no 32 bit instructions :) Now now, who was it
added the comment "Look ! A 32 bit instruction" to the code .....

Classic implementations like Z26 as it is now and Stella tend to
have speed limits if about DX100 speed, which an 18Mhz ARM
chip is probably not far off. But it can be done.