As someone else on here rightly pointed out the 6100/DOS card cabling allows you to share one display between the DOS or Mac OS environment(s)
It is possible to plug a display directly into the DOS card and get by without the cable - You lose the seamless switching between Mac OS and DOS obviously
A joystick port is also part of the 6100/DOS card connector cable
The 6100/AV has an adapter that allows the DOS card to be connected to an Audiovision display, making for an ugly tangle of wires.
The AV adapter also adds ADB, line in/out for good measure
The combined length of all these cables is more than 1 metre (if you include cable from the Audiovison display too)
On a further note, all software in the form of disk images for Apple shipped DOS cards were included on the CD titled 'Legacy Recovery' that some AASP's had access to