Re: software clock better than hardware clock

[gids.rs@sasktel.net]

> However, interrupting software clocks are incompatible with software timed
> routines, so they must have a way of counting interrupts not taken so they
> don't lose time when interrupts are disabled for more than the interrupt
> period. (Floppy disk I/O is an obvious case.)

> A 6522 has both a timer that can be used to create regular interrupts and
> another counter that can keep track of how many interrupt requests were
> made while they were disabled, so the software clock doesn't lose time. 

> Of course, long-term timing accuracy is another matter, since the
> computer's clock crystal is much less accurate than the "watch crystal"
> used by a real-time clock. 


I was not too concerned with accuracy.  My Mac, PC and IIGS all have real clocks, and I have to say only the IIGS has a fairly accurate real clock.  My PC gains about a minute a month, and the Mac loses about 1 minute every 3 months.

Also, there is the option to read the real clock every hour on the hour to update the accuracy somewhat.  Thus, the computer only works hard at reading the real clock once every 3600 seconds.

And disk I/O would never really get that far out.  Maybe a minute or two at the most out of each hour with time stamping.

I guess the main reason I did this is so I can stare at time on the screen, knowing that I wrote an efficient routine to make time fly. ":D