[comp.sys.hp] Was *this* the first RISC chip?

greg@cantuar.UUCP (G. Ewing) (03/07/89)

During a recent fit of idle curiosity, I came across some articles
describing the microprocessor used in many of HP's handheld
calculators from the HP-35 on.

It occurred to me that the design is actually quite RISCy in some
ways.  All instructions are the same length (10 bits) and execute
(I think) in one cycle (if you count a 56-bit serial shift as a
"cycle"). All arithmetic/logic operations are done in registers.

Other interesting features include a (very!) split I/D space (10 bit
ROM for instructions, 56-bit registers and data memory) and an
instruction set optimised for BCD arithmetic on various fields
of decimal floating-point numbers (mantisssa, sign, etc.)

Anyway, I think it's kind of cute. Does anyone know where I can
find out more about it? Ideally I'd like enough info to write a
simulator for it (okay, so I'm wierd). The articles I have (from
the HP Journal) don't go into much detail.

Any help appreciated,

Greg Ewing				Internet: greg@cantuar.uucp
Spearnet: greg@nz.ac.cantuar		Telecom: +64 3 667 001 x8357
UUCP:	  ...!{watmath,munnari,mcvax,vuwcomp}!cantuar!greg
Post:	  Computer Science Dept, Univ. of Canterbury, Christchurch, New Zealand
Disclaimer: The presence of this disclaimer in no way implies any disclaimer.

cruff@ncar.ucar.edu (Craig Ruff) (03/07/89)

In article <1068@cantuar.UUCP> greg@cantuar.UUCP (G. Ewing) writes:
>During a recent fit of idle curiosity, I came across some articles
>describing the microprocessor used in many of HP's handheld
>calculators from the HP-35 on.
>... Ideally I'd like enough info to write a
>simulator for it (okay, so I'm wierd). The articles I have (from
>the HP Journal) don't go into much detail.

Ah yes.  When I was a college student with nothing better to do,
I wrote just such a simulator for the HP-41C.  I got the description
of the processor and the ROM listings from the newsletter of that
calculator club (I forget the name exactly) that dug into the guts
of programmable calculators to see what was there.

Anyway, I programmed it on an HP 9825 desktop (one line display!) we
had in the chem lab.  I had to type in all of the instructions in hex
by hand (a few K!).  I got it to the point where it would
actually do stuff like the calculator would.  Too bad I didn't make
copies of the articles and the code and data files.  I could have
put it on much more powerful computers! :-)
-- 
Craig Ruff      NCAR                         INTERNET: cruff@ncar.UCAR.EDU
(303) 497-1211  P.O. Box 3000                   CSNET: cruff@ncar.CSNET
		Boulder, CO  80307               UUCP: cruff@ncar.UUCP

jthomp@hemaneh.Central.Sun.COM (Jim Thompson Sun Dallas SWAN Engineer) (03/08/89)

In article <1068@cantuar.UUCP> greg@cantuar.UUCP (G. Ewing) writes:
>During a recent fit of idle curiosity, I came across some articles
>describing the microprocessor used in many of HP's handheld
>calculators from the HP-35 on.
>... Ideally I'd like enough info to write a
>simulator for it (okay, so I'm wierd). The articles I have (from
>the HP Journal) don't go into much detail.
 

Hmm, I've got one (a HP-41 simulator), around here somewhere.
If I remember correctly, it even outputs bar-code (TeX source),
so you can load the programs into your real HP.  You could even
use 'symbolic programming' (peek & poke on the 41).  Last time I
worked on it, I was attempting a window based tool for it.
(The ultimate test would be making the goose fly backwards, no?)
Perhaps I should look at putting it together and giving it
to Rich Salz?  Naw.. who would want to run HP-41 simulations 
on their Cray?		:-)


Jim Thompson					 	jthomp@central.sun.com
"I woudn't recommend sex, drugs, or insanity 	 	Network Engineering
for everyone, but they've always worked for me."	Sun Microsystems
			-- Hunter S. Thompson

graeme@zen.UUCP (Graeme Cawsey) (03/08/89)

In article <1068@cantuar.UUCP> greg@cantuar.UUCP (G. Ewing) writes:
>
>It occurred to me that the design is actually quite RISCy in some
>ways.  All instructions are the same length (10 bits) and execute
>(I think) in one cycle (if you count a 56-bit serial shift as a
>"cycle"). All arithmetic/logic operations are done in registers.

On the Nut series of CPUs (HP-41, HP-1x), and I presume on the earlier
versions, not all instruction are one word in length.  Load immediate (LDI),
power off (POWOFF) and absolute branch (CGO & NCGO) and calls (CXQ & NCXQ)
are all two word instructions taking two cycles and the ROM fetch instruction
(RDROM) is a one word instruction that takes two cycles.

Graeme Cawsey (graeme@zen.co.uk)
Zengrange Ltd., Greenfield Rd., Leeds, England, LS9 8DB. Tel : +44 532 489048