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- Newsgroups: comp.arch
- Path: sparky!uunet!zaphod.mps.ohio-state.edu!rpi!psinntp!psinntp!trilo!sgolson
- From: sgolson@trilobyte.com (Steve Golson)
- Subject: Re: HP-9100 (was HP-97 Calculator)
- Message-ID: <1992Sep3.145432.4623@trilobyte.com>
- Organization: Trilobyte Systems
- References: <11AUG199221494044@erin.caltech.edu> <1992Aug12.150333.10293@news.uiowa.edu> <5647@armltd.uucp>
- Date: Thu, 3 Sep 1992 14:54:32 GMT
- Lines: 54
-
- In article <5647@armltd.uucp> abaum@armltd.uucp (Allen Baum) writes:
- >jones@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879) writes:
- >
- >>The diode matrix contains low level microcode [for] a digit serial processor
- >>The middle layer microcode is stored in a braided wire memory;
- >
- >I thought that the microcode was stored in an inductively coupled ROM, consisting of
- >a 14 layer pc board, where the inner layer traces defined the bits. The Russians
- >copied this calculator, which meant they had to peel back every layer of the PC board
- >to do it.
-
- Quoting from _Hewlett-Packard Journal_, v20n1, September 1968 (reprinted in
- _Computer Structures: Readings and Examples_ by Bell and Newell, 1971, also
- in _Computer Structures: Principles and Examples_ by Siewiorek, Bell and
- Newell, 1982):
-
- The control logic uses a wire braid toroidal core read only memory
- containing 64 29-bit words. ...
-
- The 32,768 bit read only program memory consists of 512 64-bit words.
- These words contain all of the operating subroutines, stored constants,
- character encoders, and CRT modulating patterns. The 512 words are
- contained in a 16 layer printer-circuit [sic] board having drive and
- sense lines orthogonally located. ... When the program ROM is activated,
- signals (micro-instructions) corresponding to the bit pattern in the word
- are sent to the hard wired logic gates...
-
- All of the hard wired logic gates are synthesized on the instruction
- logic board using time-proven diode-resistor logic.
-
- There is also a 2208 (6 x 16 x 23) bit read/write core memory for storing
- user programs and data.
-
- >The digit serial processor was extremely primitive- it couldn't add, just increment or
- >decrement a digit. Addition/subtraction was programmed from that, and multiplication,
- >division, exps/trigs/etc. programmed from those.
-
- Not exactly. The 9100A has a digit-serial, bit-parallel ALU. It can add, but
- only one BCD digit at a time. All calculations are floating point, and are
- performed digit by digit. This technique is common to many calculators.
-
- >The logic family is interesting. The boards are masses of diodes, (& resistors) packed
- >about as tightly as you could, with a few transistors here and there. It was discrete
- >DTL logic, with additional feature that one of the inputs was the power supply, and
- >it was wired up so that the input least likely to be turned on was the one connected
- >to the power supply, to conserve power.
-
- A total of 350 logic gates, containing 750 diodes and 325 resistors. My, how
- far we've come...
-
- >Allen J. Baum Apple Computer baum@apple.com, abaum@armltd.co.uk
-
- Steve Golson -- Trilobyte Systems -- Carlisle MA -- sgolson@trilobyte.com
- "As the people here grow colder, I turn to my computer..." -- Kate Bush
-