BL> Nothing happens once you get below 200 or so. The pulse just
 BL> stays 50uS wide.

 FM> Then that's the limit of the machine's ability to do all the
 FM> instructions in the interrupt service routine before another
 FM> interrupt comes along. Which surprises me.

  I've seen poory written programs like this before...  :-)

 FM> A back-of-an-envelope suggested it should be much faster.
 FM> There's only about 30 instructions in there (if it doesn't have
 FM> to call the old timer tick routine, once every 55mS. Wish I had
 FM> a bloody CRO.

  I wish I had a486DX2/66.

Regards,
Bob
___ Blue Wave/QWK v2.12
@EOT:

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