Path: utzoo!mnetor!uunet!yale!husc6!encore!devoz
From: devoz@encore.UUCP (Joe Devincentis)
Newsgroups: comp.sys.nsc.32k
Subject: Re: kit wishlist and software
Message-ID: <2864@encore.UUCP>
Date: 1 Apr 88 14:07:34 GMT
References: <880@PT.CS.CMU.EDU> <177@anumb.UUCP> <585@naucse.UUCP> <1006@ur-tut.UUCP> <23506@hi.unm.edu> <537@taux01.UUCP> <926@astroatc.UUCP>
Sender: news@husc6.harvard.edu
Reply-To: devoz@encore.UUCP (Joe Devincentis)
Organization: Encore Computer Corp, Marlboro, MA
Lines: 39
Keywords: 32k kit, cheap unix.

[eat at joes]

I had to respond to this, we have been ROMMING NS code since 1984.......


>From: johnw@astroatc.UUCP (John F. Wardale)
>Having a "link table" for each module is DEFINATLY a lossage for
>"ROM-ability" and the rest is just TOO slow!
>					John Wardale
>... {seismo | harvard | ihnp4} ! {uwvax | cs.wisc.edu} ! astroatc!johnw

Both the National guy, (with the Change one rom but not the rest story)
and johnw are out of wack here.  The cxp stuff and external procedure
descriptors are only a pain for interrupt stuff (if you can get your 
compilers to generate bsr/jsr instead of cxp rxp).

The interrupt vectors have to be "procedure descriptors", so you have to
have a module table (at least one mod descriptor large).  Since you only
have a 16 bit mod table register, it has to be in the first 64K of memory
(virtual, but for diags you run physical most of the time), so you often find
that you have to have your rom image mapped over your first 64K of address
space longer than you would like to, etc.  It depends on the particular 
application, but it is not fatal.

In the 532 you can have 32 bit addresses instead of procedure descriptors
on the interrupt table, so all of these problems go away.

Closing Editorial comments:

You can ROM cxp rxp.  It is a pain having module tables mainly because they
have to sit in a limited address space.  Interrupts with procedure descriptors
suck.  The 532 doesn't have any of these problems.  National reps on the net
tend to say the same caffeine crazed things that the rest of us say, which
means they are human too!  (This is just a rumor though :-)).  Move to bsr
and jsr and most of your rom problems go away (except the interrupt procedure
descriptors).

							devoz@encore
							Joe DeVincentis