Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!adm!milne@ICS.UCI.EDU
From: milne@ICS.UCI.EDU (Alastair Milne)
Newsgroups: comp.lang.pascal
Subject: Re: pascal microengine...
Message-ID: <11691@brl-adm.ARPA>
Date: 7 Feb 88 18:56:11 GMT
Sender: news@brl-adm.ARPA
Lines: 49


>Does that mean I can convert my LSI-11 to a Pascal Microengine??
>Where does one get the necessary chips to do this???
>I have a couple of TERAK 8510's running UCSD Pascal and it would sure be
>nice to cut out the middle man. :-)
>bill gunshannon


   The MicroEngine and the Terak are fundamentally different beasts.  Quite
   apart from the fact that the MicroEngine runs an entirely different
   microprogram, it is word-addressed, whereas the Terak is byte-addressed
   (this was to gain 128K of memory).  Also, the III.x p-code which is
   hardwired into the MicroEngine is very different from I.5 and II.x -- 
   I assume you're running one of the latter on the Terak.  Your code segments 
   would never even start to run on the MicroEngine.  (This has always been 
   the real obstacle to moving compiled p-code between machines: not the 
   differences between machines, but the differences between p-code versions.)

   Other problems: the MicroEngine has no reserved memory, whereas the Terak
   sets aside 8K as a Datamedia emulator.  This same range also serves the
   Terak as a set of illegal addresses, to trap NIL-pointer references.  The
   MicroEngine has no way of doing that.  The MicroEngine gave the p-System
   its first (very buggy) version of tasking, requiring semaphore-handling
   p-codes.  The Terak, as you well know, has no concurrency.  In contrast to
   the Terak's sophisticated interrupt structure, which allows not only
   asynchronous device I/O but asynchronous memory access, the interrupts of
   the MicroEngine are, depending on the system version, either absent,
   unreliable, or very simple.  The Terak is the only machine that supports
   the GRAPHICS: device (#3:), and the special UNITWRITE(3,...) call to
   utilise it.

   Etc., etc., etc.

   What you might to do is look around to see who might still have a
   MicroEngine they'd be willing to give or sell you.  Of the places that were
   selling them when they were being made, I imagine most are now out of
   business; but Wicat Industries in Utah made a version, and might still be
   able to help you.  Also, a friend of mine bought for himself a MicroEngine
   released by Pensee; you might try to find them.  As a long shot, you might
   even enquire of Western Digital whether they know of anybody who still has
   them -- WD never packaged them themselves: they only made the chipsets and
   disk controllers.

   Good luck.  Hang onto those Teraks -- they have virtues that have rarely
   been seen since.


   Alastair Milne,
   UC Irvine