The external cable? In which case I haven't found it yet, unfortunately.

Additional details of the 2 large chips are:
VLSI 9504MS © 1993 Apple

CHIPS F84031

I also lifted the daughtercard from it and saw:

"VIBRA 16 © CREATIVE TECH '94"

Click to expand...

Click to expand...

Vibra 16 is a PC sound chip....

Click to expand...

yep... why not?

the Houdini II PC card shipped with the 6100 has soundblaster support.

iMac600: your card is a PDS card. the connector is one for 040 PDS. the adapter thingy is an adapter from x100 PDS to 040 PDS. you can use the DOS card in a quadra series machine too.

EDIT: some better pics:

http://www.flickr.com/photo_zoom.gne?id=897649987&size=l

http://www.flickr.com/photo_zoom.gne?id=897649845&size=l

http://www.flickr.com/photo_zoom.gne?id=897484743&size=l