leblanc@godzilla.ele.toronto.edu (Marcel LeBlanc) (04/06/88)
[line eater food]
Does anybody know the EXACT clock speed of the new 1571 drives (in 1541
emulation mode)? Or for that matter, the EXACT clock speeds of the old 1571
and 1541 drives? When writting fast I/O routines, I have always assumed
that it was around 1MHz, and that the C64 has a cycle time of about 978ns (I
don't have any references nearby). I am assuming that there is a SLIGHT
difference in clock speed between the old 1541/1571 drives and the new 1571
drives, because an old routine which generated no errors in 5e+8 bytes
transfers (a test that runs in about half a day) now fails on about 10% of
bytes transfered with new 1571 drives (including most if not all C128-D's),
which means that all multi-byte transfers fail.
I have fixed the problem by slowing down the faulty routine. It now passes
the above test without any errors, with up to three devices loading the
serial bus (I haven't tried 4 devices).
Any info would be appreciated!
Marcel A. LeBlanc
University of Toronto -- Toronto, Canada
also: LMS Technologies Ltd, Fredericton, NB, Canada
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