Intellegent peripherals (was Re: MIT provides MULTICS source and documentation (DPS-8 simulation))

[Ethan Dicks]

On Wed, Nov 14, 2007 at 11:29:59PM -0500, Roy J. Tellason wrote:
> On Tuesday 13 November 2007 18:17, Cameron Kaiser wrote:
> > > An even better example is the C-64.  The disk drives on that are
> > > netoriously slow, but were computers in their own right, having a CPU as
> > > part of the drive electronics.  One trick (assuming you have at least two
> > > disk drives) was to program the disk drives to copy a disk,
> >
> > The 64 was emblematic of the best and worst features of this. The
> > intelligent serial peripherals could talk amongst each other, such as
> > the disk drive becoming commanded to TALK and the printer to LISTEN,
> > which is essentially a print spooler.
> 
> This reminds me of one particular disk-copying program,  which would have the 
> lights on both drives on solid.  You could,  once you'd kicked off a copying 
> process,  have unplugged the computer and it would just keep on going.

The PET was even better for that... in the case of the C-64, you could load
a small copier program into an unused buffer on each drive to do manage
reading and writing each sector without the C-64 itself participating, but
it meant that you couldn't then use the bus for something else, printing,
say.

Until the 2031, PET IEEE drives were dual-drive units, presumably to
amortize the cost of the intellegent controller, the power supply, the
case, over two spindles (a dual 5.25" ~170K-diskette drive was well over
the cost of the computer it was attached to in 1979, in the range of $2200).

The DOS for the 2040/3040/4040/8050/8250 drives had a "copy drive N to drive
M" command (I'd quote chapter and verse, but I don't have access to the 'net
right now).  One of the CPUs on the drive (before the 1540, there were 
multiple 6502-family CPUs in the box) would read one drive, then write
that buffer to the other drive without extra buffer copying and without
putting the traffic on the bus.  You could then, say, use your IEEE-488
acoustic coupler to logon to a BBS while disks were copying, or print to a
printer, or whatever, since the IEEE bus was not involved in that disk-to-disk
copy.

Yes, the C-64 could do it, and yes, it was cheaper than the way the PET
did it, but it wasn't the first nor was it the fastest.

-ethan

-- 
Ethan Dicks, A-333-S     Current South Pole Weather at 15-Nov-2007 at 08:21 Z
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Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html