External clock for P-I serial port?

[Yan Xiao]

In article <CHRISA.90Dec13145507 at beldar.ma30.bull.com> chrisa at beldar.ma30.bull.com (Chris Anderson) writes:
>
>Is it possible to provide an external clock for either or both of the
>serial ports on the personal Iris? 
>
>The manuals indicate that ioctl can set an external clock mode,
>but the signal is undocumented. Is the clock signal a spare pin on the 
>D connector, and if so, what should drive it?
>
>Thanks for any info.
>
>---Chris A.

I am wondering why you need an external clock?  gettimeofday() provides
time in micro-second.  

xiao