.TH read_t0() "" "" "Internal Kernel Routine"
.PC "Read the system clock t0"
.B "int read_t0()"
.PP
.B read_t0()
reads channel 0 (t0) of the programmable interval timer (\fBPIT\fR),
which drives the system clock.
A system clock tick is the time it takes timer t0 to decrease from 11,932
to zero.
A driver can read the timer whether interrupts are masked or not,
and receive a number between 11,932 and zero.
Each unit, therefore, represents a little less than a microsecond.
Overhead per call to
.B read_t0()
is about five to ten microseconds,
depending upon speed of the CPU and clock speeds
of the system upon which a program is being run.
.SH "See Also"
.B
internal kernel routines
.R
