The secrets of the Wondermega MIDI port and it's custom bios explored by Sudden
- Thread starter Mr^Burns
- Start date
Chilly Willy
Established Member
Yes, MIDI on a 7.67MHz 68000 is kinda tricky without a bit of help from the hardware... particularly on receiving. The Amiga had an issue with the built in serial port and MIDI in that it had no buffer for receive data. You either responded to the serial interrupt fast enough to not lose data, or you were hosed. The problem there came with what mode you ran in... the more colors you used with the desktop, the more DMA contention you have to deal with, to the point that using high-res sixteen color desktop meant you could only respond to serial in the horizontal or vertical blank periods. That tended to cause dropouts in the receive data, so most MIDI apps on the Amiga either recommended no more than eight color desktop, or to use a zorro serial card with a properly buffered read data port. Transmitting isn't quite as critical, but at the (relatively) low baud rate MIDI ran at, a complex song could drive the MIDI right to the edge of what the serial rate could handle, and then you ran into that DMA contention issue again on the Amiga, but for sending instead of receiving. Again, lower the colors, or get a decent serial card.
Is the serial port on the WonderMega interrupt driven? Can you tell? Or is it just polled? At least the SegaCD doesn't have DMA contention to deal with. Sega did a good job of making sure that bus contention in general was minimized on the MegaDrive system and peripherals.
Is the serial port on the WonderMega interrupt driven? Can you tell? Or is it just polled? At least the SegaCD doesn't have DMA contention to deal with. Sega did a good job of making sure that bus contention in general was minimized on the MegaDrive system and peripherals.
