Re: Randy downloaded KESYS


Robert Wessel wrote:

... M$ file time base is 01.01.1980
Only for FAT. NTFS stores the number of 100ns periods since 1-1-1601.
I see, and I'm not fully through with my NT-reader yet.
But where is this 100nS timer ?
I wont believe that NT let the PIT fire IRQs at ~10MHz rate.

The PIT is limited to 1.19318 MHz anyway :)

What happened on 1.1.1601 ?
An olde Greek raised his middle finger (digit) for the first time ? :)


There isn't one. Usually NT, et al, run with no faster than a 1KHz
timer. The stored format is units of 100ns, and that's the format
returned by the basic APIs, although there are functions to convert
those to other formats, including UTC, system time (y/m/d/h/m/s/m) and
DOS.

The old 32 bit formats (both *nix 32 bit number of seconds and DOS
16+16) were clearly too short, both in terms of resolution and the
covered period, so the question was clearly how to use a 64 bit
number. Clearly 1ns would leave too short an overall period, but I
always wondered why 100ns instead of 1us, not that it really matters,
of course.

I would certainly not be surprised if some of those unused bits of
resolution eventually got used, especially if PCs ever develop better
clock hardware (something along the lines of S/370s time-of-day
clock).

The Time stamp counter could be used for it (with some overhead).

When I decided the time date format for my own FS I figured out
that 2 Sec intervals (like FAT) will not be enough on 'newer' HDs,
I checked on various compressed formats but finally I just did it
the lazy way and took the RTCL BCD-output and appended it with the
century high-nibbles and an 0...999mSec (PIT setting @ 04ABh =~1mS;
synchronised every Second).

But isn't this fine granular timing mainly needed for determination
of the age of temporary files (like pending jobs/buffers) anyway ?
The user or an application would hardly replace files within every 1 mSec.

__
wolfgang



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