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From: pf@csc.ti.com (Paul Fuqua)
Newsgroups: comp.arch
Subject: LISPMs not RISC? - Re: CISCy RISC? RISCy CISC?
Message-ID: <61665@ti-csl.CSNET>
Date: 23 Oct 88 03:35:33 GMT
References: <16921@ames.arc.nasa.gov>
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Organization: TI Computer Science Center, Dallas, Texas
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    Date: Friday, October 21, 1988  8:26pm (CDT)
    From: raymond at pioneer.arc.nasa.gov.arpa (Eric A. Raymond)
    Subject: LISPMs not RISC? - Re: CISCy RISC? RISCy CISC?
    Newsgroups: comp.arch
    
    This is where TI ends (I believe) and Symbolics goes on (the tags that is).
    At least that's where the CADR (LMI and TI didn't really vary from this
    design)  left off.

Not true.  The Explorer 1 (can you say retronym?) has some ability to do
type checks in parallel, and the Explorer 2 has even more.  My first
assignment back in 1984 was to update the arithmetic microcode to use
it.  LMI may not have varied much (I really don't know), but TI did a
little with the 1 and quite a bit with the 2.

				       They also did things like go to larger word
    sizes (36 & 40) and CDR coding (I don't think CADR had this - might be wrong).

CDR-coding did exist in the CADR -- it was a microcode phenomenon, not a
hardware one.
    
							  Note that both
    RISC and LISPM-chip (read stack machine with tag bits) are vague terms.

One CADR paper I have makes the careful distinction between the CADR
machine, which is a microprogrammable 32-bit general-purpose processor
with some fancy features, and the Lisp machine, which is the engine plus
the microcode to run Lisp.  The distinction has blurred in later
designs, what with the Ivory containing Lisp microcode in ROM and the TI
chip having some hardware recognition of macroinstructions.

                              pf

Paul Fuqua
Texas Instruments Computer Science Center, Dallas, Texas
CSNet:  pf@csc.ti.com (ARPA too, sometimes)
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