CDDA not playing correctly at 50Hz

Ask anything your want about Mega/SegaCD programming.

Moderator: Mask of Destiny

Post Reply
Posts: 36
Joined: Wed Dec 07, 2011 2:09 am

CDDA not playing correctly at 50Hz

Post by Bitybity » Sat Jul 27, 2013 12:22 am

Hello everyone.

I have a friend, who tests my game on his SegaCD.
He have an American SegaCD, but his TV only supports PAL color mode, so, in order to run it, I have to send him a USA version of my hack, and once his console boots up at 60Hz, with a switch, he moves his console back to 50Hz so it shows up the colors.

The game works ALMOST perfectly... except for the CDDA. Once the game tries to load a CDDA track, it doesn't seem to play, and after some minutes it crashes.
However, he told it doesn't happen with the original games, only mine. And mine only works correctly if ran at 60Hz.

Any ideas of what is going on?

Here is the Sub-CPU section of the code:

Chilly Willy
Very interested
Posts: 2849
Joined: Fri Aug 17, 2007 9:33 pm

Post by Chilly Willy » Sat Jul 27, 2013 5:49 pm

Supporting European SCDs is easy - just use the EU security binary blob instead of the US. Also, vertical blanks will be 50 Hz, and you should still be generating the level 2 int to the SCD in the vert blank. I suspect it crashes due to an issue between what it expects for timing and what you're generating due to booting in 60 Hz mode - failure to correctly generate the level 2 int at the right frequency WILL crash the SCD after a short period.

Post Reply