> Thanks, I found it about 3 hours after I sent my prev msg.
> Just out of curiosity, are there any ideas about why that
> value was chosen?
>From my copy of "ISA System Architecture", a manual describing
PC/AT-compatible PCs (i.e., PCs prior to EISA, Microchannel, VESA Local
Bus, and PCI):
Chapter 24
Prior To This Chapter
The previous chapter described the numeric coprocessor
interface and floating-point emulation.
In This Chaper
This chapter describes the system timers incorporated in
all ISA-compatible machines.
-------------------------------------------------------------------
The System Timer, Timer 0
The System Timer, Timer 0, is a programmable frequency
source. A 1.19318MHz signal provides its input clock
rate. You can specify a divisor to divide into the
input clock to yield the desired output frequency. ...
1/(1.19318*10^6) = .838096*10^-6, i.e. 1.19318 MHz is one cycle every
.838096 microseconds.
The classic Sniffer was a notebook PC with Network General's software
running on top of DOS, but "running on top of DOS" doesn't prevent you
from whacking the PC system timer to keep whatever time you want,
including setting the divisor to 1.
I seem to remember reading some Sniffer documentation that (partially)
described the classic Sniffer file format; I think it gave the various
time unit code values as
0 Unspecified - default by network type
1 "PC" - 0.838096 microseconds
2 "3Com" - 15 microseconds
3 "Micom" - 0.5 microseconds
4 "Sytek" - 2 microseconds
I suspect that "PC" means "we used the PC's timer to time-stamp
packets", and that "3Com", "Micom", and "Sytek" refer to using a timer
on network interfaces from the company in question to time-stamp
packets.
> Other than cussedness? Seems goofy
> that NG would force the use of floating point into something
> as basic and pervasive as measuring time.
Blame IBM, or maybe Intel, depending on who specified the system timer
input signal frequency. :-)
