How fast is the Arduino?

Well I'm going to attempt and control 192 outputs simultaneously (8x8x3 leds).

I'm sure the Arduino can handle that fairly easily. The question is how well will stuff like software PWM work? I dont actually have mine yet so I cant tell its speed easily.

Options: A) Hopefully if its fast enough I'll be able to talk to a computer in a different protocol, translate it to the 595's protocol and do PWM all at the same time. I know how to optimize it so my code will be fast but its a massive amount of work.

B) Make the computer give the data to it in as similar to the 595's protocol as possible. That way it only needs to proxy data and apply PWM.

C) Toss the idea of emulated PWM out the window.

Which one is more realistic? Also would getting a 20mhz crystal help?

Check out, there might be source there you can hack - plenty of people there play with LEDs and Arduinos. Check out youtube as well, keyword "arduino" I've seen lots of 8x8's set up doing all kinds of wonderful things, there might be something useful there you can adapt.

Arduino essentially runs at the raw speed of the ATmega CPU chip used, which is pretty fast. Still, I don’t know whether it’s up to doing 192 channels of flicker-free LED dimming PWM; that’s a pretty expensive task… How many brightness levels?

How many brightness levels?

Obviously not a lot. 4 or 8 would satisfy me well.