"Toy" computers (was Re: Micro$oft Biz'droid Lusers)

From: Cameron Kaiser <spectre_at_stockholm.ptloma.edu>
Date: Fri Apr 26 11:40:20 2002

> Actually, I don't remember what CPU was in the 1541 drives, but I
> seem to recall that it was actually more powerful than the computer.

More like "about the same" -- the 1541 is a 1MHz 6502, and the C64 is also
approximately 1MHz (slightly less for PAL, slightly more for NTSC).

The 1571 is 2MHz IIRC, but then the 128, which was its intended controlling
machine, can also run at 2MHz.

Many of the PET drives had multiple 650x CPUs, each handing different aspects
such as FDC operation, GCR coding, etc. When the 2031 and the 1541 arrived,
Commodore assigned all the tasks to one overworked CPU instead -- the CPU
alternates between FDC and IP mode on interrupts.

> I also remember somebody working on a way to get code into the drive
> to be executed, but that's kind of fuzzy.

That's easy to do with M-W/M-R commands to alter drive RAM; it's just slow
to do transfers back and forth over the IEC bus, which fouls any useful
attempt at cooperative processing (best to hand the drive a separate task
to do all on its own), and there's not much RAM there -- only a few kilobytes,
most of which is being used by the drive itself, of course.

Several monitors featured "transparent" access to drive RAM where the
monitor would treat drive RAM as if it were main memory. The communication
speed, of course, invariably wrecked the otherwise clever illusion.

----------------------------- personal page: http://www.armory.com/~spectre/ --
 Cameron Kaiser, Point Loma Nazarene University * ckaiser_at_stockholm.ptloma.edu
-- Not sun-worshippers: Son-worshippers! -- Uhura, Star Trek "Bread & Circuses"
Received on Fri Apr 26 2002 - 11:40:20 BST

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