CBM engineer Bil Herd has given some details on the weaknesses of the C64/C128/VIC-20 expansion port (with a little bit on TED computers, like the Plus/4). To read what he says, go to the bottom of the discussion at
http://www.vintage-computer.com/vcforum/showthread.php?19192-3-Slot-Expansion-Card-Comments-Requested
Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
The Other Group of Amigoids
http://www.calweb.com/~rabel1/
Southern California Commodore & Amiga Network
http://www.sccaners.org