From: sclawson@bottles.cs.utah.edu (steve clawson)
Date: Sat, 15 Jun 1996 12:01:48 +0800
To: declan+@CMU.EDU (Declan B. McCullagh)
Subject: Re: PBS show
In-Reply-To: <IlkDlaO00YUy1ODDgK@andrew.cmu.edu>
Message-ID: <199606141734.LAA11581@bottles.cs.utah.edu>
MIME-Version: 1.0
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Declan B. McCullagh uttered:
> I remember the Commodore 64
> drives (1541?) that were just plain slothful.

     Anyone else remember a program called TurboTape that Compute!
magazine published?  It actually made loading from tape faster than
from a 1541!  One of the cool things about the drive was that it used
GCR recording and had a variable number of sectors per track
(increasing as you went from the middle to the edge of the disk), so
it was able to fit around 180k per side!

     Commodore had some good drives on their PET's, but good old Jack
got burned by the fact that there was only one supplier of the cables
for the interface (IEEE-488, or [GH]PIB) and swore that they'd develop
their own. =) So for the VIC-20 they came up with a serial interface,
but because of problems with the chip they were using (6522 VIA) they
could only recieve a _bit_ at a time. =) On the C-64 they replaced
this chip with one that didn't have the problem (and thus could have
waited until it grabbed 8 bits from the serial line before bothering
the processor), but that would have meant they would have had to
redesign the drive...  Unfortunately, the increased demands of the
video hardware in the C-64 meant that they couldn't keep up with the
drive anymore!  So, in a stroke of genius, they slowed down the
transfer rate. =(

     The Atari 8-bits also used a serial bus for perhipherals, but at
least it ran at a (only somewhat moderately) respectable 9600bps. =)
Unfortunately their drives used the clunky 4:4 encoding for data, so
only held 90k per side.


steve

-- 
// stephen clawson				sclawson@cs.utah.edu
// university of utah