While I could do some experiments to try to determine the behavoir I was wondering what best practise is.

I'd like to add a 65C22 to my micro for the purpose of:

Generic parallel IO via a header; or
2 9 pin joystick ports

(Amongst other things, like the timers and serial input to a keyboard.)

I read (not on the datasheet) that inputs float high. So is it reasoanable to not use external pullups? With external pllups I can't make the port general purpose (ie. useable for outputs via the header when the joysticks aren't plugged in.)

If I need external pullups I'll probably scrub the joystick ports, since putting the 2 ports on general purpose headers sounds more useful.

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On non-WDC VIAs, inputs offer an LSTTL load. This is true even of 65c22's from Rockwell. An unconnected LSTTL input is basically high. The loading presents a problem for some applications. I definitely recommend using WDC's which not only have true CMOS inputs, but also bus-holding devices, so floating inputs are not a problem.

WDC's also have very strong output drivers. I have tested Rockwell and WDC 65c22 outputs here, and they are many times as strong as the data sheet says (and I believe the processor has the same output circuits). In my experiment, WDC's outputs were able to pull to within 0.8V of either rail with a 220-ohm resistor to the opposite rail, meaning a 19mA load, even pulling up, and give 50mA into a dead short. Rockwell's could pull down with 100mA into a dead short, but could not pull up as hard, not being symmetrical like WDC's.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?