Atari ST diskettes
paulkoning at comcast.net
Mon Dec 7 15:23:59 CST 2020
> On Dec 7, 2020, at 3:17 PM, Chuck Guzis via cctalk <cctalk at classiccmp.org> wrote:
> On 12/7/20 11:50 AM, Van Snyder via cctalk wrote:
>> One of my friends changed the tables in a 1620 to do octal arithmetic,
>> for telemetry processing.
>> Speaking of those tables, do you remember why the 1620 was called
>> CADET? Not because it was a "beginner's" or "novice" computer. It was
>> an acronym for "Can't Add; Doesn't Even Try."
> That was the Model I; the Model II had the math tables hardwired.
> Several options were available (and required for some software), such as
> indirect addressing and hardware floating point. A close relative was
> the 1710; basically a 1620 with interrupts, real-time clock and various
> options for ADC/DAC interfaces for process control. I believe that
> binary arithmetic was also an option, but I'd have to check.
> Dijkstra developed a dislike for the thing pretty early on. One of his
> big gripes was that you can't write (to peripherals) everything that you
> read. The other gripe was that there were certain "untouchable"
> characters that you could neither test for nor use in arithmetic nor
> create, except by reading them (e.g. numeric blank, 8-4 punch).
I remember him writing (dismissively) about the 1620, don't remember him discussing the 1710. The 1620's obvious issue, apart from the ones you mentioned, is the blocking I/O. Can't write a multiprogramming system on such a machine. Dijkstra worked on the first commercial machine that had interrupts standard (the Electrologica X-1). So he knew how to use and benefit from interrupts; his Ph.D. thesis is an example.
> The standard disk drive was the 1311.
I remember those. Ours had two, and a disk O/S that used them. ("Monitor II"?) One day the system drive developed a leak, spraying hydraulic oil all over the system pack. IBM repaired the leak, bled the hydraulics, and cleaned the pack and heads (with high purity isopropyl alcohol I scrounged from the chemistry department stock room). Booted up fine afterwards. Don't try that with modern disk drives. :-)
> As much as the haters bashed it, it was a pretty reliable workhorse for
> the time and a great system for learning fundamentals. (absolutely
> uniform instruction layout; no user-addressable registers--all
> memory-to-memory), decimal and no fixed word length.
> Was there ever a magnetic tape drive for the 1620? I don't recall ever
> hearing about any. That alone would make it unique among IBM
> offerings--card and disk, but no tape.
Not that I know of. They did offer paper tape, though that wasn't on ours.
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