17 Nov
2007
17 Nov
'07
1:42 a.m.
On Sat, Nov 17, 2007 at 12:40:25AM +0000, Tony Duell wrote:
I've never seen a 2031, but all the
GPIB-interfaces double drives contain
2 processors I think.
The 2031 is very much like a 1541, but with an IEEE-488 interface rather
than C= IEC.
The 8050/8250 contain a pair of full 6502s, one to
handle the disk data itself, the other the run the DOS and talk to the
GPIB port. They communicate via shared memory, IIRC 4K of it (the unit
uses the well-known trick that a 6502 only drives the address lines when
the clock input is in one of its states, so by feeding inverse clocks to
the 2 processors you can easily get them to interleave access to memory).
Prior to the 8050/8250, I think the arrangement was one 6502 to talk to
the bus, and one 6504 to talk to the drives, but in other respects, the
same.
The control processor ROM is in one of those 6530
RRIOT chips, which
makes replaicng it a little problematic...
I have, I think, a full set of 2040 ROMs, including the right 6530, but
most of my pre-8050 drives were originally 2040s that were later upgraded
to the same ROMs as a 4040 (the only difference AFAIK is the label on the
outside).
although my 8250LP (half-height
drives, plastic case) has a daughterboard in the 6530 socket containing,
IIRC, a 6530, the ROM part of which is never addressed and a normal ROM
chip, along with a very little glue logic.
I have seen those daughterboards before.
In all the GPIB dual drives that I've seen, therre
is a separate
'analogue board' containing the motor control circuits, the read/write
chain, etc.
Yes.
The serial-interfaced drives used in the C64 processor
contain a single
processor (6502 in all that I've seen) and have all the electronics
(apart from the spindle motor control) on one PCB.
Yes... serial-interfaced drives and the 2031.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 17-Nov-2007 at 01:30 Z
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Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html