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From: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Newsgroups: net.micro
Subject: Re: Need a microprogramming consultant!
Message-ID: <1820@sdcrdcf.UUCP>
Date: Wed, 6-Mar-85 13:32:11 EST
Article-I.D.: sdcrdcf.1820
Posted: Wed Mar  6 13:32:11 1985
Date-Received: Sun, 10-Mar-85 05:15:18 EST
References: <1272@drux3.UUCP> <501@ahuta.UUCP> <184@redwood.UUCP>
Reply-To: darrelj@sdcrdcf.UUCP (Darrel VanBuer)
Organization: System Development Corp. R+D, Santa Monica
Lines: 23
Summary: 

Another reason to have microprograms in RAM (besides reducing cost of bug
fixes) used by a number of companies (notably those making Lisp machines) is
tailoring the instruction set of the machine to the application E.g. the
Xerox Dolphin can be an Alto, a Lisp machine, a Smalltalk machine or a Mesa
machine, depending on which microcode is (dynamically) loaded.  The Alto
code is straight emulation to exploit a preexisting operating system, the
others implement an abstract machine model tailored to the language.
The Dolphin has only a single processor, but has a small read-only
microprogram memory which contains just enough to bootstrap microcode from
the disk or Ethernet.
Some computers and vendors provide tools for user microcode (usually for
augmenting the instruction set rather than replacing it), a few even
implement virtual memory microstores!

-- 
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
...{allegra,burdvax,cbosgd,hplabs,ihnp4,orstcs,sdcsvax,ucla-cs,akgua}
                                                            !sdcrdcf!darrelj
VANBUER@USC-ECL.ARPA