Music not working properly for Turbo Out run with 8521 CIA

[yellperil]

On the current core 21-10-25 and a long way back ( for instance it also has the exact same behavior in the C64_20210617.rbf core ).

The music for Turbo Outrun is broken when using the 8521 CIA .

When you switch to 6526 CIA the music works properly.

[HarborSeal]

According to comments on a youtube video, the original hardware had the same issues.
https://www.youtube.com/watch?v=qG82RMyS07Y

Andrew Brown - Shame my c64c never played the samples properly back in the day..

Phonolith303 - @Andrew Brown my C64C, too.
It's because later C64s contained a 8580 MOS Technology SID Soundchip with different volume handling: as noise reduction, the volume was turned down if there was almost no output (similar to a noise gate).
Because samples were a trick of programming, the soundchip "thought" that there was no output, turned the volume down and made the samples barely audible.
First C64s (like mine) had a 6581 chip and played samples correctly.

[yellperil]

Hi there,

Thanks, yes I am aware of the SID and sample issue on the original hardware, I have a number of C64C's.

The issue is with the alternate CIA the 8521.
When you switch to 8521 CIA the music does not work properly for either SID ( that is both the 6581 and the 8580 ).
When you use the 6526 CIA the music is fine on both SID chips.

This was an issue with the CIA in the core originally where the timing was incorrect in the CIAs HDL.

Cheers.