[rescue] systems with user modifiable microcode.

[Greg A. Woods]

[ On Wednesday, October 2, 2002 at 15:06:30 (-0400), Dave McGuire wrote: ]
> Subject: Re: [rescue] systems with user modifiable microcode.
>
> On Wednesday, October 2, 2002, at 02:52 PM, Greg A. Woods wrote:
> > The PDP-11/60 has a microcode option.  I think it is the only one of 
> > the
> > PDPs that had such a feature.  I'm not sure about VAXen.
> 
>    The 11/03 does as well.

Hmmm... I have one of those!  :-)

>    While its intended use is different, it does amount to 
> runtime-modifiable microcode.  (not trying to start another of our 
> famous flame wars here, Greg)

Well, OK, sort of, though the Alpha docs are careful to always say that
PALcode is just a set of subroutines written using normal instructions
which are (usually) resident in main memory and they also consistently
say that the PALcode provides a mechanism to implement consistent
low-level system support functions without having to use microcode.
Even the DEC guys compare PALcode more to the BIOS in a PC than anything
else.

I guess the only big difference with something like a BIOS is that
PALcode is directly supported by the instruction set and you can call
PALcode subroutines as if they were instructions, and from a software
point of view that sure does make it look a lot like microcode than just
a set of subroutines.

-- 
								Greg A. Woods

+1 416 218-0098;            <g.a.woods at ieee.org>;           <woods at robohack.ca>
Planix, Inc. <woods at planix.com>; VE3TCP; Secrets of the Weird <woods at weird.com>