microcoding a PC into a PDP-11 (was: RE: Classic Computers vs.

From: Zane H. Healy <healyzh_at_aracnet.com>
Date: Tue Sep 18 22:08:07 2001

> Does anyone on this thread even understand microprogramming?
>
> Apparently not.
>
> Pentium CPU's can't be microprogrammed, unless your Intel. Even microcode
> updates cannot replace the basic instruction set.
>
> If you write a program in Pentium assembly code to run PDP-11 instructions, you
> have just written an 'emulator', even if it does not run under windows.
>
> But an writing such an emulator is not 'microprogramming'.

I was wondering about this! In all honesty I don't see any reason to go
this low level, by doing this you're making it less portable. Ideally you
want something like a stripped Linux or QNX system sitting on top of the
hardware, with the system emulator sitting on top of that. If you want to
avoid UNIX altogether, just take simh, and set it up so that it's started
when the system boots, and you boot all the way up to the OS of your choice.
Go one step further and hack simh so that if you shutdown the OS running on
top of simh, that it shuts down the host OS.

If you want to do hardware, go with FPGA's and reimplement the CPU and
controllers like Neil Franklin is trying to do with the PDP-10. The tricky
part here of course being the disk and tape controllers (unless you want
to write your own device drivers).

                        Zane
Received on Tue Sep 18 2001 - 22:08:07 BST