I'm writing some OPL2 code. I was trying to stay away from using the old "increment a timer counter and check vs. the old value" method of timing writes to the OPL2, but when I set my playing code as the interrupt handler, it plays 20-30% slower than it should and there's quite a bit of jitter. Changed it to increment a counter and check it in the main loop instead and now it plays perfectly.

Did I do something wrong? Not sure what best practices are concerning interrupt handlers and if they really should do as little as possible.