Re: load average patches for MiNT 1.10 + patches

[Darryl Piper <drpiper@cix.compulink.co.uk>]

In-Reply-To: <23994.9403051221@earth.ox.ac.uk>


>>
>>I say use the VBL routine to check your timer, but check the 200 Hz
>>timer from in their. That way your one second timer will be accurate to
>>either 1/50, 1/60, 1/70 second. This will cut down on system overhead,
>>which is in my opion becoming too much for 8 MHz 68000s.
>
>The overhead would not be significantly affected by moving the routine to
>the VBL, if anything it would be increased, see my original version of
>loadave for more details. Also, you are most likely to have clock drift due
>to the inaccuracy of the test's timing.
>
>The bulk of the routine is only called once per second, every other 1/200th
>of a second a counter is merely decremented and tested, this is about 5
>instructions I believe, not much of an overhead at all.


Ah but what I ment was,  with-in the vbl routine don't increment your own
timer variable, but on startup take a snap shot of the _hz_200 var and
calculate your effitice time from that, thus at most you will only be 1/50
second out.



>From experiments, the increase in overhead is so little that I couldn't
>measure the speed difference on my 520STM with 2.5MB RAM. (This is not my
>development system.. I use my TT and Sun 3/80 for that.)

But dont' forget MiNT is designed to be compatible with STs, and with
everything new going into it their has to be a lose somewhere. IMO hitting
the _hz_200 counter routine is calling it either four times too much
( 4/200 = 1/50 ) or downto three times too much.( 3/200 :==: 1/70 ).
As your timer was only ment to be accurate to the second, a change of
magnitude of one is fine, ie accurate to 1/10 second. dont you think ?

Bye now,

  Darryl

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