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Re: Apple disk drive...
- Subject: Re: Apple disk drive...
- From: Michael J. Sch�lke <mjschuelke@hotmail.com>
- Date: Sun, 4 May 2003 22:25:59 +0200
- Newsgroups: comp.sys.apple2
- Organization: n/a
- References: <8uVsa.41493$3h5.660259@news2.east.cox.net> <b918us$k52$1@freenet9.carleton.ca>
- Reply-to: web0301@mjschuelke.de
- Xref: archiver1.google.com comp.sys.apple2:30168
Michael Black wrote:
> One reason the Commodore (and at least some Atari) drives are slow
> is that they are connected to the computers via a serial port.
> That tends to be relatively slow, if for no other reason than that
> the bits go one at a time rather than in parallel.
No -- the CBM drives are slow because the serial port is controlled
directly by the processor, shifting out the bits in software, rather
than using a hardware shift register.
This was introduced as a workaround for a bug in the VIC-20's 6522 VIA,
kept in the C-64 for compatibility (even though the bug was fixed in the
6526 CIA), and only remedied in the C-128 in combination with the
1570/1571 drives.
Regards,
Michael