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freebsd/sys/isa
Bruce Evans 49a116737e Estimate an initial overhead of 0 usec instead of 20 usec in DELAY().
I have code to calibrate the overhead fairly accurately, but there
is little point in using it since it is most accurate on machines
where an estimate of 0 works well.  On slow machines, the accuracy
of DELAY() has a large variance since it is limited by the resolution
of getit() even if the initial delay is calibrated perfectly.

Use fixed point and long longs to speed up scaling in DELAY().
The old method slowed down a lot when the frequency became variable.
Assume the default frequency for short delays so that the fixed
point calculation can be exact.

Fast scaling is only important for small delays.  Scaling is done
after looking at the counter and outside the loop, so it doesn't
decrease accuracy or resolution provided it completes before the
delay is up.  The comment in the code is still confused about this.
1997-01-29 22:51:44 +00:00
..
ic Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
atrtc.c Estimate an initial overhead of 0 usec instead of 20 usec in DELAY(). 1997-01-29 22:51:44 +00:00
fd.c Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
fdc.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
fdreg.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
joy.c Updated #includes to 4.4Lite style. 1996-09-10 08:32:01 +00:00
kbdio.c - Modified for PC-98. 1997-01-16 14:56:16 +00:00
kbdio.h Upgrade the kbdio rutines to provide queued kbd & mouse events. 1997-01-15 18:16:32 +00:00
kbdtables.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
rtc.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
sio.c Fixes and workarounds for Hayes ESP: 1997-01-29 21:50:02 +00:00
sioreg.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00
syscons.c Add save/restore cursor as pr SCO screen(HW) manpage. 1997-01-23 20:00:45 +00:00
syscons.h Add save/restore cursor as pr SCO screen(HW) manpage. 1997-01-23 20:00:45 +00:00
timerreg.h Make the long-awaited change from $Id$ to $FreeBSD$ 1997-01-14 07:20:47 +00:00