Lisp, the machine language. Was Re: Hallelujah!

From: Eric Smith <eric_at_brouhaha.com>
Date: Sun Apr 4 18:18:15 1999

> For example, if you
> pulled the ROMs on the 11/45 and reprogrammed them, you'd not be able to
> make the machine into a P850 (for all they are both 16 bit machines, and
> both have 16 machine registers). The PDP11 instruction set uses some
> 3-bit fields to select registers, and those bitfields are connected (via
> logic) to the register select lines in the CPU circuity. The microcode
> can't change that.

Actually, the microarchitecture of the 11/45 is Turing-complete, so you
could in fact make it run P850 code. It just wouldn't be particularly good
at it.

Just two weeks ago while researching something else, I found an old product
announcement for a third-party writable control store option for the 11/45.
However, in order to make this option more usable, they also added several
new data paths to the 11/45.
Received on Sun Apr 04 1999 - 18:18:15 BST