microcoding a PC into a PDP-11 (was: RE: Classic Computers v s. Classic Computing)

From: Carlini, Antonio <Antonio.Carlini_at_riverstonenet.com>
Date: Thu Sep 20 04:53:59 2001

Bill Pechter wrote:
> Actually much of the 11/780 microcode is in rom.
> The stuff loaded from RX01 is mostly bug fixes to the rom code.
> The patches went into the Writeable Control Store board.

The VAX-11/750 did the same thing (IIRC the
first microcode patch required a large number
of roms to be changed by field service ...
the control store was redesigned to allow
patchable code a-la 780).

> The 11/785 went to completely RAM loaded microcode.
> The 11/780 did have an optional second User Writeable Control Store
> board.

In one or other of the DTJ articles, the
development of the MicroVAX II is described.
They used the VAX-11/730 with new microcode
to simulate a MicroVAX II: the 11/730
was *completely* soft.

Antonio
Received on Thu Sep 20 2001 - 04:53:59 BST