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 Post subject: EASy68K timer interrupts
PostPosted: Sun Jan 24, 2010 5:04 am 
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Joined: Mon Dec 27, 2004 11:40 pm
Posts: 318
What's the granularity of the timer interrupts? Experiments I've done suggest that it is 10ms. Setting the timer to any value not a whole number of tens of ms seems to set it to the next whole 10ms interval.

Code is here. Here are the results. Figures are ms timer interval followed by actual measured 10,000 ms delay.

Code:
EASy68K output log file: 24/01/2010 02:32:08

 100  10000     80  10010     60  10030     40  10020     20  10340
  99  10120     79  10180     59  10160     39  10250     19  10600
  98  10310     78  10250     58  10330     38  10540     18  11150
  97  10320     77  10420     57  10520     37  10810     17  11780
  96  10410     76  10570     56  10750     36  11140     16  12560
  95  10520     75  10660     55  10940     35  11450     15  13360
  94  10610     74  10810     54  11110     34  11780     14  14300
  93  10820     73  10980     53  11360     33  12220     13  15420
  92  10910     72  11140     52  11540     32  12540     12  16680
  91  10910     71  11160     51  11620     31  12830     11  18070
  90  10000     70  10030     50  10020     30  10010     10  10020
  89  10100     69  10160     49  10210     29  10450      9  11130
  88  10270     68  10310     48  10420     28  10730      8  12560
  87  10370     67  10440     47  10660     27  11300      7  14310
  86  10450     66  10660     46  10870     26  11700      6  16780
  85  10640     65  10790     45  11110     25  12140      5  20040
  84  10720     64  10940     44  11370     24  12620      4  25160
  83  10820     63  11140     43  11670     23  13070      3  33410
  82  10990     62  11290     42  11910     22  13730      2  50110
  81  10950     61  11390     41  12130     21  14160      1  100200

Is this 'feature' peculiar to my computer or is it EASy68K?

Lee.


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PostPosted: Tue Jan 26, 2010 2:14 pm 
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Joined: Thu Dec 16, 2004 6:42 pm
Posts: 1102
The timer used is the C++ Builder Timer component. The Timer component probably uses the low Resolution Windows timer and is also limited by the Windows message loop. 10mS resolution would be about what I would expect.

All current PCs have a high resolution timer. It should be possible to use the high resolution timer in a high priority thread to increase the timer resolution. I would think resolutions approaching 1mS would be possible. Feel free to add an item to the wish list if this is something that would be desired.

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Prof. Kelly


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