diff options
| author | Thorsten Lockert <tholo@cvs.openbsd.org> | 1996-02-25 23:03:17 +0000 |
|---|---|---|
| committer | Thorsten Lockert <tholo@cvs.openbsd.org> | 1996-02-25 23:03:17 +0000 |
| commit | 915abd18d665696c222321f6c34870ebed9a5457 (patch) | |
| tree | 8879e4bd855cc89da55753b81fb094b329021735 /sys/arch/i386/isa/clock.c | |
| parent | d9458b4cd30074b84a2c9949cbbf2aaecd954409 (diff) | |
Allow use of Pentium cycle counter for high-precision time keeping;
from FreeBSD
Diffstat (limited to 'sys/arch/i386/isa/clock.c')
| -rw-r--r-- | sys/arch/i386/isa/clock.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/sys/arch/i386/isa/clock.c b/sys/arch/i386/isa/clock.c index 5cacb8cc9fc..2833d2f2f10 100644 --- a/sys/arch/i386/isa/clock.c +++ b/sys/arch/i386/isa/clock.c @@ -107,6 +107,10 @@ WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. void spinwait __P((int)); +#ifdef I586_CPU +int pentium_mhz; +#endif + #define SECMIN ((unsigned)60) /* seconds per minute */ #define SECHOUR ((unsigned)(60*SECMIN)) /* seconds per hour */ #define SECDAY ((unsigned)(24*SECHOUR)) /* seconds per day */ @@ -303,6 +307,19 @@ findcpuspeed() delaycount = (FIRST_GUESS * TIMER_DIV(1000)) / (0xffff-remainder); } +#ifdef I586_CPU +void +calibrate_cyclecounter() +{ + unsigned long long count, last_count; + + __asm __volatile(".byte 0xf, 0x31" : "=A" (last_count)); + delay(1000000); + __asm __volatile(".byte 0xf, 0x31" : "=A" (count)); + pentium_mhz = ((count - last_count) + 500000) / 1000000; +} +#endif + void cpu_initclocks() { |