"Wayne M. Smith" <wmsmith_at_earthlink.net> writes:
> I have a Lisa 2/5 with H8 ROM which has the following
> I/O card, no. 820-4033-A:
> http://home.earthlink.net/~wmsmith/_uimages/Lisa_IO_820-4033-A.jpg
This card works in a Lisa 1, Lisa 2 (no hard drive), and Lisa 2/5 (external
profile). It has support for two floppy drives, although that only works
with Twiggy drives. It does not support an internal hard drive.
> Some time ago I came across a different I/O card, no. 820-4033-A2:
> http://home.earthlink.net/~wmsmith/_uimages/Lisa_IO_820-4033-A2.jpg
That card works in a Lisa 2/10 or Macintosh XL. It supports one 400K
3.5 inch drive (or 800K with Sun Remarketing's modified firmware), and
one internal Widget hard drive.
The two cards are not interchangeable. The Lisa 2/10 and Macintosh XL
use a different backplane. IIRC, the connectors are offset so that
the old I/O card will only plug into the old backplane, and the new
I/O card into the new backplane. But even if I'm mistaken about that,
I'm rather more certain that the cards aren't electrically interchangeable,
since I've been looking at the schematics just recently.
Among other differences, the floppy drive motor speed control is done
differently. The old I/O card was designed to serially shift the motor
speed control byte into the disk drive; when they upgraded to the 400K
3.5 inch drives, they had to add a "Lisa Lite" adapter card to convert
the serial bits into a PWM signal. The new I/O card generates PWM on
the card.
The old I/O card had a socket for an AMD 9511 (or 9512) math coprocessor,
which was never used by any production Lisa (or Macintosh) software.
The new I/O card instead has a footprint (but usually not a socket) for
a Western Digital WD2001 DES crypto chip, which also was never used by
any production Lisa or Macintosh software.
There are other minor differences between the two cards; I haven't bothered
to track them all down.
Eric
Received on Sat May 13 2000 - 19:28:52 BST
