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| From: Rachy (all posts)
Date: 1998-05-18
Subject: Re: VICE vs C16
|
> >I am not sure about the 7502/6502 differences, but we are not going to
> >have more than one CPU implementation in the emulator. The current one is
> >well tested and fits perfectly in the current setup. Adapting other CPU
> >implementations will probably take more work than it's worth.
>
> The cycle timings in the plus/4 are diff since its got 2 speeds, does
> this cause any problems?
It may cause problems, because of the timer-based decoders used in some of the "newer" programs (after 1993). If they switched into the normal timing ($ff13 - 0. bit on as I remember), then there should be no problem at all, but some coder (for the better protection :) used
$ff1e, $ff1d, and waits until those reach some value, then starts decoding. This may cause problems, because most of the timing will slide away, and decoding produce a wrong code. (If high timing is active, then all the opcodes run under almost half time than the original, because timers are counting TED's clock cycles in place of CPU's cycles.)
Bye:
Rajnai Almos
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