Much will depend on why you need it. I am not familiar with the derivative you used, but "clocking out" or "shifting out" a byte at a higher rate than 57600 could be possible, you ll have to check the data sheet. The problem is sustaining that rate or a higher rate for more than 1 byte. If you send out a byte with 1 start, 1 stop and 8 bits, no parity, you effectively will need 10/56700 or 174 us. That means that your processor will have to present a new byte to the shift register every 174 us.

So, do you just want to send out a single byte at a higher speed than 57600 bps? If so, what's the use?

Or do you want to send out a byte-stream at a speed of 57600 bps? That would only be possible if your program can stick to the above timing... (which should be feasible if you only need to send the contents of a memory buffer).

So, in order to give decent advice, "We need more information." as Jez already said..

and by the way: I would call it bit rate, not baud rate... It's better (I think) to keep the term Baud rate for the signal in between the modems. (but that topic was already discussed in another thread..)

regards

Patrick