Originally Posted by Ami_GFX
Here is the list of MIDI interfaces for the Amiga:
Every one of them uses the serial port which limits multiport bandwidth considerably. Almost all the the Multiport expanders for the ST, Mac and PCs of that era use a faster port. The ST expansion units use the cartridge port except for the Export which C-Lab warned against using for timing critical applications that used a lot of bandwidth like doing a lot of mod wheel changes or multibyte sysex messages in a sequence. Note ons and offs which are 3 byte mesages would be fine. The same would hold for the Amiga MIDI interfaces. If you did something that was complicated and used a lot of data, the timing would break down. That is why you would want additional ports. The ideal midi setup for an Amiga would have a Zorro card with additional serial ports and multiple midi interfaces. That would deal with any hardware timing issues.
MIDI expander for ST connect to ROM port coz ROM port is directly connected to MC68000.
It would be quite easy to test MIDI timings on Amiga and ST today if somebody have both. Make complex midi setup and try both with same midi song.