6581 pulse + sawtooth - incorrect samples for oscillator MSB = 1
Versatile Commodore Emulator
Brought to you by:
blackystardust,
gpz
The 6581 pulse + sawtooth samples were obtained around 25 years ago. At the time, it was not known that the oscillator MSB can be zeroed via combined waveforms. The following program takes this fact into consideration, and obtains correct samples for the complete waveform:
https://github.com/daglem/reDIP-SID/blob/master/research/pulse-saw.a65
https://github.com/daglem/reDIP-SID/blob/master/research/pulse-saw.d64
It would be helpful if others could run the .d64 to obtain samples from different 6581s. The 6581 samples in reSID are comparatively strong (more non-zero values than average), and it would be nice if we could get samples which more or less match the existing ones (for MSB = 0).
Here are the samples I got from the machine I had set up, converted for inclusion in reSID:
https://github.com/daglem/reSID/blob/master/src/wave6581_PS_.dat
https://github.com/daglem/reSID/blob/master/src/wave6581_PS_.h
These are good enough, and can be replaced later if someone comes up with "better" (stronger) samples.
updated the sample in r43932
leaving the ticket open since we still need more/better samples :)
BTW, shouldn't this be done for ST and PST too? Every combination that include sawtooth, on 6581, is affected by the problem.
good question!
Good point!
Here is an updated sampling program for all combined waveforms (takes forever to run, unfortunately).
https://github.com/daglem/reDIP-SID/blob/master/research/combsample.a65
https://github.com/daglem/reDIP-SID/blob/master/research/combsample.d64
Forwarding from Trurl
@daglem have a look :)
I guess the r4ar 3488 would be the best replacement in reSID.
Test results (combsample.d64) for the 6581 in my C64 attached. It has quite lame combined waveforms.
Samples (combsample.d64) from lots of chips from Trurl: