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Re: PC to Apple II disk drive
- Subject: Re: PC to Apple II disk drive
- From: "Michael J. Mahon" <mjmahon@aol.com>
- Date: Fri, 23 Jun 2006 18:21:19 -0700
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- Newsgroups: comp.sys.apple2
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Linards Ticmanis wrote:
Linards Ticmanis wrote:
The problem with the Apple drive is, it wants to send or receive one bit
exactly every 32 microseconds.
Two errors here: it's one byte every 32 microseconds, which means one
bit every 4 microseconds.
And though it may be possible to *write* an Apple disk directly through
a parallel port (if all interrupts are disabled), it is *not* possible
to sample fast enough to unambiguously *read* an Apple disk.
Regardless of processor speed, the legacy I/O system of the PC precludes
getting sufficiently high speed access (2MHz samples) using the
traditional parallel or serial ports.
And it's not "exactly" but a bit less. One "Apple microsecond" is about
1.020484 real microseconds.
Actually, its the reciprocal of that: 0.9799 microseconds/cycle.
-michael
Parallel computing for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
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