#1882 Wrong emulation on reSID 6581

[bozz64]

Playing /MUSICIANS/H/Huelsbeck_Chris/Katakis.sid in Vice on reSID 6581 gives wrong audio output compared to the output of a real 6581.

Interesting is that the audio output for this tune on reSID 8580 in Vice is much more close to a real 6581.

Just focus on the snare output on voice 2 and it will be clear that is not like it should be. The issue is not related to the filter.

I tried the latest Vice and a few older version like 3.5 but they give the same result.

Attached are two recordings, one from the output of Vice 3.7 using a reSID 6581 and one from a real C64 using a real 6581.

[Leandro Nini]

Interesting finding! It's related to [bugs:#1436]
This patch fixes both the test and the tune:

diff --git a/src/resid/wave.cc b/src/resid/wave.cc
index 7cee96d15e..e5dda1e0be 100644
--- a/src/resid/wave.cc
+++ b/src/resid/wave.cc
@@ -27,7 +27,7 @@ namespace reSID

 // Number of cycles after which the shift register is reset
 // when the test bit is set.
-const cycle_count SHIFT_REGISTER_RESET_START_6581 =    9768; // 0x8000
+const cycle_count SHIFT_REGISTER_RESET_START_6581 =   35000; // 0x8000
 const cycle_count SHIFT_REGISTER_RESET_BIT_6581   =    1000;
 const cycle_count SHIFT_REGISTER_RESET_START_8580 = 2519864; // 0x950000
 const cycle_count SHIFT_REGISTER_RESET_BIT_8580   =  315000;

[gpz]

So should i aplly this to trunk? :)

[Leandro Nini]

Yep! The tune confirms the problem, the patch solves both bugs.

[gpz]

applied in r43784, thanks!