The 8088 issues the 0x38 RETURN_FROM_INT command to the 7201 at the end of the ISR, but that causes z80_irq_reti() to hit the "Failed to find an interrupt to clear IE0 on" message and so the interrupt isn't cleared.

As far as I know, the alternate clear is only for the 8274, not the uPD7201, but I could be wrong.

Last edited by R. Belmont; 07/24/14 04:17 AM.