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Re: 200Hz SNDH-replay using TimerC
Posted by: Splash/S1 May,29.2015-00:58 

Interesting.

YM reg#7: I guess the GPIO bits of the YM are exclusively updated by the TOS using the system timer at 200Hz.

How the SNDH SID voice players can cope with that knowing that the SID voice interrupt may be more prioritary than the timer C and might happen just right after the TC system function selected a YM register but right before it wrote or read the data? (which means that the OS won't do the expected access when coming back from the interrupt hence the risk of bugs). Do they analyse the instruction that has been interrupted using its address on the stack to ensure it was not a YM access and if necessary reselect the register before leaving the interrupt?

I thought also: maybe some system features linked with the IO bits of the YM could be temporarily "cleanly" stopped with system calls before playing a music (e.g. stop keyclicks) to decrease the probability of system calls to access YM registers. Well I don't think there is any system call such as "please don't use the floppy drive" or "put my IDE in sleep" though...

On Falcon there may be actually a solution: copying the whole TC interrupt from ROM to RAM, then simply patch the OS code so as to be able to monitor when YM accesses are done. Would need to locate the whole ROM code and relocate it in RAM after patching it. Anybody tried? ;)

Is MiNT still using this old 200Hz System timer vector, or does it defines its own vector with hopefully a better way to handle the YM?

mmhhh...more questions than answers in this message ;)







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Topic Posted by  Date 
200Hz SNDH-replay using TimerC Sdw May,21.2015-15:31
  Re: 200Hz SNDH-replay using TimerC gwEm/PHF May,21.2015-16:00
    Re: 200Hz SNDH-replay using TimerC Sdw May,21.2015-16:16
      Re: 200Hz SNDH-replay using TimerC evil May,21.2015-18:40
        Re: 200Hz SNDH-replay using TimerC Sdw May,27.2015-16:39
          Re: 200Hz SNDH-replay using TimerC evil May,27.2015-17:52
            Re: 200Hz SNDH-replay using TimerC Sdw May,27.2015-23:58
              Re: 200Hz SNDH-replay using TimerC gwEm/PHF May,28.2015-16:42
                Re: 200Hz SNDH-replay using TimerC evil May,28.2015-17:16
                  Re: 200Hz SNDH-replay using TimerC Splash/S1 May,29.2015-00:58
                    Re: 200Hz SNDH-replay using TimerC evil May,29.2015-11:56
                      Re: 200Hz SNDH-replay using TimerC gwEm/PHF May,29.2015-15:13
                        Re: 200Hz SNDH-replay using TimerC Splash/S1 May,31.2015-19:21
                  Re: 200Hz SNDH-replay using TimerC Sdw May,31.2015-21:49
                    Re: 200Hz SNDH-replay using TimerC insane Jun,07.2016-10:08
                      Re: 200Hz SNDH-replay using TimerC insane Jun,07.2016-10:29
                      Re: 200Hz SNDH-replay using TimerC Splash/Sector One Jun,30.2016-18:30


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