FWIW. the
programamble machine that I've worked on that I consider to be
the most elegant is the HP9100B calculator (never worked on a -A). That
machine is glorious inside.
Care to expand a little bit, I know next to nothing about early HP
calculators and computers.
Sure. This may techncially be off-topic (in that the machine was sold as
a calcualtor), but since said machines can run user programs, have s
storage device, can interface to peripherals, etc, it's hard to think of
a sane defintion of 'computer' that excludes them and that doesn't also
exclude things that are classed as computers.
Anyway, HP calcualtors... There are a couple of websties to look at for
more inforamtion :
http://www.hpmuseum.org/ is mostly for the handheld machines
http://www.hpmuseum.net/ is for the larger machines and has a lot of
manuals to download.
The HP9100 was HP's first electronic calculator (I specify it like that
becuase there were some cpecial slide rules shipped with HP RF
instruments to calcualtor reflection coeffficients, etc). It is a classic
example of a point I was making in another tread. The component count is
quitree small (under 1000 transistors). There are no digital ICs (there
are 8 op-amps o nthe magnetic card reader PCB, but nothing in the
processor/mmemory sections). The compoonets are themselves simple. But
the way they are interconnected is very complex.
BAscially, the machine is a special-purpose processor. It's microcoded
(64*29 bit core-on-a-rope microcode). The main program ROM is an
inductively coupled PCB ROM, with 512 locatiosn of 64 bits each. There's
a total of 44 flip-flops in the machine (again very small), 43 JKs (40
for the processor registers, including the program counters for the
microcode and main ROM, 2 in the clock divider and oen to select the user
program memory page. And a single SR flip-flop to drive the error
indicator. The flip-flops are interconencted by diode AND and OR gates
(no NOTs, although both the Q and Q/ (E and F in HP's terminology)
outputs of the flip-flops are used.
Tehre isn;'t even a a ful ladder. To add 2 registers, you incremeent one
and decrememtn the other until the second has got to 0 (seriously).
User memory is a little core plane, 6 bits wide (I forget how many
lcoations). A location can store amongst other thigns, a digit (4 bit BCD
+ sign bit + blanking bit) or a user program keystroke (there happen to
be 64 differnt keycodes...)
Amazingly this machine is a full prgramamble ccientific calculator. The
dispaly is a little CRT displaying 7 segemt digit patterns. There's a
magneitc card reader you cna use to store your programs on and reload
them later (although. of course the core memeory is non-volatile) adn a
periperhal conenctor that will give you serious headaches if you try to
use it.
The machine is often claimed ot he RPN. I feel it isn't. There are 3
registers, X, Y,Z which appear to eb a stack, but there is no automatic
lift and drop. Keyboard intput goes into X, the 2-numer operators like
'+' act as Y:= Y + X, X being unchanged. OF corse there are keys to flit,
drop and roll the stack, but that doens't make it RPN to me .
OK ,that's the first one (more info on request). The next series are
knwon as 98x0 or 9800 machines. They are all based roudn the same 16 bit
bit-serial processor built from abotu 80 TLT ICs.
The HP9810 is essentially the same ot the user as the 9100. 3 level
stack, etc. The memeroy is now volatile 1103 DRAMs, so the magnetic card
reader becomes very imporntant. There's slso the option of a built-in
thermal strip pritner. Amaxingly, although it uses ICs, the 9810 is
larger than the 9100, and doesn't do as mauch in its basic form (there
are no transcendental functions, you have to add a ROM module for that).
The dispaly is now 3 rows of LED digits (a total of 45 digit positions)
for the 3 stack registers.
The HP9820 is essentially the same machine but usign an infix notation
langaage (so you cna acutally do 2+4 and get the answer 6. Many of the
PCBs are the same as those in the 9180, and theothers have
closely-related circuitry. It has twice ans much ROM firmware and a 16
character alphnumeric display.
The big brother of this family is the HP9830. It has the same processor
boards, but everyhtign else is differnt, although somewhat simuilar in
design. It has a full QWERTY keyboard, a 32 character alphanumeric
display and runs BASIC. It's a fairly simple ABSIC, with no string
operations, but it's BASIC. And you could get add-on ROM modules to add
strings, matrices, advanced I/O, etc. There's a built in digital
cassette drive to store programs and data in numbered files, there was
even a hard disk unit as a peripheral.
The HP98x5 machines are something of a hotch-pptch. The 9805 is a
non-programamble machine that took plug-in modules (the statistcis module
is the only remotely common one). I have never seen this machine, I
beleive it's closyl related ot e HP46 and HP81 printign calcualtors, and
uses the same processor (custom 'Arithmetic and Registers' and 'Control
and TIming' ICs). The 9815 is the only old HP calculator to use a
stnadard CPU -- a Motorola 6800. This machine is a bit like an overgrown
HP97. It's a 4 level stack RPN machine (now with automatic lift and
drop), it's prgramamble, it has a built-in printer and cartridge tpae
drive. The HP9825 used an HP custom BPC processor module (a ceramic
hybrid circuit under a massive heatsink) and runs a language called HPL
which is essentaily an extended version of the HP9820 programming
language. The HP9845 is a twin-procesosr (user program an I/O) machine
running BASIC and with a CRT display. It's pusing it to call that oen a
calculator.
What more can I tell you? Well that depends on what your are interested
in. I could bore you to death by talking aobtu the fetch-execute cycle of
the 9800 procesosr, for example.
-tony
