Re: Reject 6502 Cycle Counter?

["Michael J. Mahon" <mjmahon@aol.com>]

Bryan Parkoff wrote:
>     I have read Intel documentation which it explains Performance Counter 
> like time stamp.  Apple II Emulator requires to execute 6502 CPU to 
> increment 6502 cycle until 6502 cycle reaches 17030.  Then Screen Update 
> checks to see if it is 17030 6502 cycles before screen is updated.
>     If I attempt to program Apple II Emulator by ignoring 6502 cycles, I 
> would expect that 6502 CPU run faster than 1MHz while Performance Counter 
> tells Screen Update to check for millisecond timing (1/60 frames per 1 
> second).  It may be inaccurate speed.
>     What do you think?

It depends on what you're trying to achieve.

If you want to update the screen every 1/60 second of _emulated_
time, then use the cycle counter as you describe.

If you want to update the screen every 1/60 second of _real time_,
then use a timer (or a VBL notification if refreshing at 60Hz).

-michael

Music synthesis for 8-bit Apple II's!
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