Suna

CASIO fx-5500 Scientific Calculator

"Factoring made easy" by Casio in 1986!

Was this CASIO fx-5500 the first ever calculator in the market able to do symbolic calculus (formula manipulation), otherwise known as C.A.S. these days?

This is a handy little machine, almost of the same size and form as the HP Voyager series, although featuring totally different capabilities and operation philosophy.

Main features, based on the user manual:

24 digit LCD with 5x7 dot matrix alphanumeric capability.
Analog contrast adjustment.
Constant Memory.
Power supply: 2xCR2032

True algebraic logic operation. Replay for easy editing

Display: 10 digits mantissa and 2 digits exponent.
Internal: 12 digits mantissa and 2 digits exponent.

Each result is rounded to 10 digits for display

Stack sizes:

Manual operations: Numeric 8 levels, command 20 levels.
Formula manipulation: Numeric 15 levels, command 20 levels.

Input buffer size for each entry: 79 steps storage area for numbers and commands

Memories:

3 x Formula memories (I, II, III). Each up to 79 steps.
12 x Register memories (A to L)

34 functions

Symbolic calculus (Formula manipulation):

Expansion
Factoring
Simplify

Solver (one unknown quadratic and linear, three unknown linear)

Forensics test
arcsin (arccos (arctan (tan (cos (sin (9) ) ) ) ) ) result: 9.000007164
The same result as the Casio fx-730P among others.
Doing (9-Ans) *1000000 to find additional internal digits gives just 7.164.

Using some expressions from the user manual examples to test the symbolic manipulation.
Well, it is not a powerful machine and we can't even consider it a C.A.S. system, but in 1986 it was something rare to see on a pocket calculator.

Simplify 5X^2 + 7X - 6 - 3X^2 + 2X + 9
Took about 2 seconds to find this result: 2X^2 +9X + 3

Just for fun, tried Expand (X + 3)^5
Took about 8 seconds to find this result: X^5 + 15X^4 + 90X^3 + 270X^2 + 405X + 243

Back cover.
Power supply: 6VDC, 0.01W

Yet another Simplification test, using large exponents:
Simplify 2X^6 x 3X^7 x 5X^89 + 3Y^8 - 7Y x 6Y^3
Result: 30X^102 + 3Y^8 - 42Y^4

And another with huge exponents,incuding negative ones.
Simplify 3X^9000 x 7X^-76543
Result: 21 / X^67543
(about 1 second to compute this)

Small detail concerning the superscript font used for exponent for number "2".
If using the dedicated key "x^2" it will use a different font than the one used for all the exponent digits when using the key "x^ n"

Tear down for inspection.
Serial number suggests a date of 1986, February (6B).
Removing the aluminum back cover by undoing tho screws reveals the metallic sliding battery cover.

Removing the inner plastic frame by undoing eight self taping screws. Lift it at the battery side first, then use a plastic pry tool to unlatch the remaining sides leaving the display side to the end.
Note the grounding/shielding spring at the lower left side, interconnecting the front face plate and back cover to the circuit common ground.

The PCA is free to be removed. Lift it on the battery side first, then gently pull the display assembly to remove it from the front cover bed.

Unfolding the display flat cable to uncover the main PCA components:

- Hitachi HD61747B32 6B 23 HM47B-32 Processor (1986)
- Hitachi HD61747B33 5M 13 HM47B-33 Processor (1985)
- NEC D1004G (uPD1004G) NM390 6527KK 4K 4-bit words or 2KByte SRAM memory (See note below).
- Toshiba 4071BF 86 10HB CMOS Quad 2-input OR gates

Can't find information on the NEC uPD1004G IC.
However, Kyoro's Room Blog documents the Casio PB-770 internals and we know that it uses four of these chips for a total of 8KByte of SRAM memory.

The Hitachi HD61747 processors are used in several Casio models, only changing the firmware code. For example:

- fx-5200P:
Hitachi HD61747B16
Hitachi HD61914C 1KByte static RAM

- fx-4000P:
Hitachi HD61747B38
HD61914 8kbit static RAM

- FC-200:
HD61747B55
HD61914 1KByte static RAM.

-PB-120:
HD61747B57 9L 13

- PB-500:
HD61747B05 5K 13
HD61747B06 5H 13