"intelligent" disk drives

[Ethan Dicks]

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
South Pole Station
PSC 468 Box 400       Temp  -40.9 F (-40.5 C)   Windchill   -67.2 F (-55.1 C)
APO AP 96598          Wind    9.1 kts Grid 97   Barometer 681.8 mb (10560 ft)

Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html