Activity for Dag Lem
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Dag Lem posted a comment on ticket #1887
Samples (combsample.d64) from lots of chips from Trurl: Hi! Here are the new results for my chips, organized in directories this time. Trurl
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'broken r4ar 3789.dat.txt' and 'cbm 4383.dat.txt' are almost identical to the chip I tested. 'broken r4ar 3488.dat.txt' is closest to (slightly weaker than) Andreas Boose's 6581 0683. 'broken 0384.dat.txt' seems to have extremely strong samples. I guess the r4ar 3488 would be the best replacement in reSID.
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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
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You'll have to sort this out without me :) All of this has been tweaked considerably since I last worked on it, so I can't comment on it. I can however say that there is no such thing as a "correct" DC level - this varies considerably between chips, at least for the 6581. But maybe you can get closer to some kind of average?
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Use the new fast noise LFSR reset by Dag Lem to improve the tests
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Use new fast noise LFSR reset, patch by Leandro Nini (see bug #1885)
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I have tested the patch on a C64, and there is still a minor issue - badlines disrupt the timing of the LFSR clocking in noisewriteback/noise_writeback_check.asm and wb_testsuite/noise_writeback_check.asm Changing the start of both files to the following fixes the issue: ; disallow interrupts and disable screen to get stable timing sei lda #0 sta $d011 sta $d015 raslo: bit $d011 bpl raslo rashi: bit $d011 bmi rashi I haven't tested wf12nsr.asm, but I think it should be changed like this: ; disallow...
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Even though the result is the same, I think I would still set the frequency immediately before releasing the test bit in wb_testsuite/noise_writeback_check.asm, so that one isn't fooled into thinking that the setting before the noise reset makes any difference. Other than this nitpick, this looks good to me :-)
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Just a final small nitpick :-D In the Makefiles, you could set NEWRESET=0 just once, and then use that as -DNEWRESET=$(NEWRESET) in the recipes. This would make it simpler to override the setting.
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I believe you should set the desired frequency in noise_writeback_check.asm and wf12nsr.asm just before clearing the test bit, otherwise the oscillator will start running earlier than without the changes, and you'll be changing the tests ever so slightly.
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One more thing - set_lfsr_18_22 is timing sensitive, so make sure that no badlines or interrupts can interfere. I'm guessing all the tests already ensure this, but I mention it anyway - better safe than sorry :-)
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Nice! I think you may be missing a final setting of the test bit in noise-reset_new.asm, i.e. something like this at the end (the first part of point 4 - reset_lfsr, in the original program): LDA #$08 STA $D412 After this, the clearing of the test bit in the test programs will finalize the reset.
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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.
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6581 pulse + sawtooth - incorrect samples for oscillator MSB = 1
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Make sure to fetch the program again after reading this, it has been fixed to restore the I flag after calls to CHROUT.
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