Re: Amiga delay implementation

[Frank Wille <frank%phoenix.owl.de@localhost>]

Michael L. Hitch wrote:

>> After reviewing the old delay() from 4.0 I have to agree with Ignatios
>> that there is not much reason to change the old calibration loop
>> method, except Michael has some arguments for it.
>
>   I do?

I thought you replaced the old delay() intentionally.


>> BTW, what happens when the old delay-loop is interrupted? It will
>> become longer? That would be an argument for Michael's new delay()
>> implementation.
>
>   It's not my implementation - it came with the timecounter diff, and
> since I didn't experience any problems with it, I didn't look closely
> at it other than noting in passing that the old delay()/DELAY() had
> been replaced.

Oh. I didn't know. The log shows your name for all new timecounter stuff. :)


>   As to going back to the cpu delay loop, interrupts would change the
> amount of the delay, so the delay could be variable.  The current
> implementaion should be less affected by interrupts, although could
> also delay longer depending upon how long the interrupt processing
> takes.

Ok. That's exactly what I found out as well. So in the end there is a small
argument for replacing the calibrated loop. Although I'm sure it performed
much better for very small delays.

Who decides about it? Ignatios?


>   I don't know how accurate the clock frequency on the Draco and don't
> know if the currently delay() implementation would be accurate enough
> to work on the Draco [once the current delay() implementation is
> correctly fixed].

I have never seen a DraCo myself, but from the source it seems that the
Quicklogic chip in a DraCo rev. 4 has only a frequency of eclockfreq/7,
which makes it difficult to be more precise than 10 us.

The old method would be much better for DraCo.


>   The other question would be how many Dracos are still running NetBSD?

That doesn't matter, IMHO. I like NetBSD because support for old hardware
usually isn't dropped.


-- 
    _  Frank Wille (frank%phoenix.owl.de@localhost)
 _ //  http://sun.hasenbraten.de/~frank/
 \X/   Phx @ #AmigaGer