10 Apr
2005
10 Apr
'05
1:11 p.m.
Ethan wrote:
The difference was that the computers ran at a
nominal
8MHz
7.8336 MHz (divided down from 15.6672 MHz crystal).
(less effective speed due to video-induced bus
blockages),
About 15-20% less, effective.
and the printers ran at 12MHz.
12.5 MHz, if memory serves.
In 1987-88 I worked on a design for an accelerator for the LaserWriter,
using a 68020 processor and faster 32-bit wide DRAM. The hardware was OK,
but it took too long to reverse engineer enough of the firmware to patch
the exception handlers to deal with the '020 exception stack frame format.
The project was cancelled before completion.
Instead we built an adapter to use ADB keyboards and mice on the
pre-ADB Mac models, or the early keyboards and mice on the ADB Macs.
It was called "ADBridge". Not many sold. Unfortunately I don't have
one any longer.
Eric