\ Real Time Clock                                                    vandys
\ Requires Pentium rdtsc instruction
only drivers definitions

code rdtsc ( -- du )   $0F c, $31 c, \ rdtsc -> eax, edx
   eax push   edx push   next c;
$70 constant IO_RTC
$00 constant RTC_SEC
$0A constant RTC_STATUSA
   $80 constant RTCSA_TUP
create tsc1sec 0 , 0 ,   create tsc1msec 0 ,

: (rtcin) ( port -- u )   IO_RTC outb   $84 inb drop   IO_RTC 1+ inb
   $84 inb drop ;
: (wait_tup) ( -- )   begin   RTC_STATUSA (rtcin)   RTCSA_TUP and 0= until ;
: (wait_sec) ( sec -- sec' )   begin   (wait_tup) RTC_SEC (rtcin)
      2dup - if   nip exit   then   drop again ;
: calc_tscfreq ( -- )   (wait_tup) RTC_SEC (rtcin)
   (wait_sec)   rdtsc dnegate rot   (wait_sec) drop rdtsc d+
   2dup tsc1sec 2!    1000 um/mod tsc1msec ! drop ;

only

Put this all in "drivers"

Quick and dirty rdtsc access

I/O port base for controlling RTC
RTC seconds counter
RTC status register A
 Status: time updating, don't look
Calculated number of CPU ticks per second, and millisecond
 NB: 1sec is a 64-bit count, 1msec only 32-bits
: (rtcin) Play nicely with the HW, pull in an RTC register

: (wait_tup) Wait for the timer to be out of an update window
: (wait_sec) Wait for the second counter to bump from the passed one
 to something else... generally the next second
: calc_tscfreq Watch our RTC to get a one second interval, record
 the delta in the rdtsc CPU cycle counter to get (approximately) the
 number of CPU ticks per second, and millisecond