As others have said, the main culprit is probably the U8 CIA chip, since that handles floppy,serial and half the parallel port.
The other CIA (U7) also handles a bit of the floppy port,parallel and also joystick ports, So try playing a game to see the port works with a joystick.
If you can, try printing something. If the joy/mouse ports work OK, but printing doesn`t,it looks like the U8 is faulty.
If printing doesnt work, and you have joy/mouse problems, then U7 could be at fault.
If both of those work OK, I`d suspect the Paula chip (handles sound,serial,floppy and joyports), does sound play OK on your 600?
I doubt very much that you`ve damaged the Gayle chip. The CIAs are first in line to get blown if you short something across the ports at the back.
If Gayle was damaged, you`d probably have a whole lot more problems than you`ve described, ranging from IDE or PCMCIA problems to even the Amiga not booting..
