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Re: A new pseudo-disk for Apple 2.
Linards Ticmanis wrote:
Michael J. Mahon schrieb:
And NMI is not a fully "recoverable" interrupt, either, not to mention
its ability to kill real disks if writing...
The disk bit is clear - interrupt in the middle of writing a sector, and
at worst the whole track will go to never-never land.
(I knew what you meant, and never for a milisecond worried that
the "disk bit" might get accidentally set. ;-)
But how exactly is a NMI "non recoverable" on the Apple? On the
Commodore that is not the case AFAIK, so I don't think it's a property
of the 6502. (Never refrain from refusing to have more than three
negatives in a sentence ;-)
In my mind, there has always been a "red flag" associated with the NMI,
possibly because of exceptional conditions related to its occurrence
during a BRK instruction.
Upon review, it seems that the only issue with NMI on an Apple II is
potential disruption of critical timing (as in the case of 5.25" disk
access) and the usual problem with not being able to discover the state
of softswitches on machines prior to the //e, so that memory and display
use potentially cause loss of state.
Of course, the "blind softswitch" problem applies equally to IRQ.
-michael
New, faster SUDOKU v2.0 solver for Apple II's!
Home page: http://members.aol.com/MJMahon/
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