I’ve been hunting for 48 bit computers - and found a few. Let me know of any I’ve missed…
I found a few in “A Third Survey of Domestic Electronic Digital Computing Systems” a huge 1961 document from the Ballistic Research Laboratories. From there, for starters, here’s the transistor-based Philco 2000:
Here’s a video about Philco and their machines:
Now let’s see what’s in the Third Survey that merits a 48 bit description - detailed technical descriptions and some photos and diagrams at the links:
- SAC Data Processing Subsystem AN/FSQ 31 (V) from IBM with 48 bit words plus 2 parity bits and offering 6 bit bytes
- AN/FSQ 32 again from IBM… same model? Certainly very similar
- Control Data Corporation Model 1604 a 48 bit word with means to access 24 bit subwords
- Datamatic 1000 Electronic Data Processing System has a 52 bit word with 48 data bits and 4 check bits
- Honeywell 800 has 48 plus 6 check bits. “Designed for general purpose business, business-scientific, and scientific applications, system capable of running eight programs simultaneously.”
- MANIAC II (Mathematical Analyzer Numerical Integrator and Computer Model II) is tube-based, has 4k words of core storage and 12k of CRT storage. “Average error-free running period: Several Hours”
- MANIAC III is transistor-based, more than twice the performance.
- MERLIN just over 1000 tubes, 8k words of electrostatic barrier grid tube storage
- NAREC Naval Research Electronic Computer uses 1300 tubes, has 16k words of core, has 48 bits and packs two instructions per word. Needs 31 staff to offer two-shift access, at about 85% availability.
Philco Transistorized Automatic Computer (TRANSAC S-2000) as seen in video above. 20k transistors. 4 microsecond add time (variable.) “There is one 48 bit register, three 24 bit registers, and up to 32 optional index registers. The program section has asynchronous logic. Automatic assembling and compiling system called TAC”
- PHILCO CXPQ Philco Transistorized Automatic Computer CXPQ. 5500 tyransistors, 4k words core, 16k words drum, 45 microsecond add time, 7 index registers.
The B5000 was designed to be an Algol machine.
So the worlds greatest computer expert returned to Europe and told his friends about the amazing B5000 Algol system. They decided to order three B5000s.
The Burroughs Large Systems Group designed large mainframes using stack machine instruction sets with dense syllables and 48-bit data words. The first such design is the B5000 in 1961. It is optimized for running ALGOL 60 extremely well, using simple compilers. It evolved into the B5500.
And from West Germany, from 1964 to 1971, we have “the Telefunken TR440, a machine with a 48-bit word length”
I also found some info on the use of 48 bits as a floating point data size:
The historic English Electric KDF9 computer used a floating-point format very similar to that of the IBM 7090 computer, except for being adapted to its 48-bit word length.
One solution would be to use 48-bit integers, and 48-bit and 96-bit floating-point numbers, as the ICL 1900 did
The Scientific Controls Corporation 660 computer also used, as its normal floating-point format, the full 48-bit format shown in this section of the diagram.