I'm interested in using the Mac IIci's serial port at 128,000bps.

I hear this is possible by supplying an external clock (there is a little
box where I can enter in the frequency [in the booter]).

Does anyone have any information on how I'd go about using the serial port
at this speed?  What type of clock to give the serial port?

If you could, please send me any info.

HSKi and GPi are valid clock inputs?

Thanks,
Grant Stockly