Phill Harvey-Smith wrote:
Indeed, though I do remember there being problems with
using the very
early 1540 drive from the VIC with later models, as the timing was not
compatible with the C64. I believe that the only real difference
between the 1540 and 1541 drives was slightly different firmware,
cirtainly the drives look identical inside. I also believe that the
1540 can be upgraded by replacing the firmware with that from the 1541.
There was
also a command or sequence of commands that could be sent to a
1540 that changed its timing to meet the C64 requirements, until the
next time the 1540 was power-cycled or otherwise reset. When I got my
first C64 in 1982, it came with that information, but I no longer have it.
I am of the impression that on a VIC one would get slightly higher
performance out of a 1540 than a 1541, but I don't know for sure. And I
don't know whether there is a corresponding command or sequence that can
be sent to a 1541 to switch it to 1540 timing.
Eric