Happy DEC-20 Day!

Chuck Guzis cclist at sydex.com
Sun Dec 20 16:48:46 CST 2009

On 20 Dec 2009 at 17:04, William Donzelli wrote:

> > I kind of suspected that was the case. Did anyone make a large 48
> > bit machine?
> CDC 1604. CDC 3600. Maybe more.

A google on "48 bit word" turns up the following:

"Incidentally, a somewhat larger number of computers had a 48-bit 
word length; some of them had 24-bit instructions, others 48-bit 
instructions, and some had variable-length instructions: the Control 
Data 1604 and 3600, the Honeywell 400, 800 and 1800 (and their 
progenitor, the Datamatic D1000), the Philco 2000 (whose central 
processor could have been the Philco 210, 211, or 212, and which was 
therefore sometimes referred to as the Philco 2000 Model 212 with a 
Philco 212 central processor), the RCA 601, the Maniac II, the AN/FSQ-
31 and AN/FSQ-32, which were both made by IBM for the U.S. 
government, the Elliot 4130 (later the I.C.L. 4130), the FACOM 202, 
the University of Manchester Atlas, and the I.C.T. Orion are 
computers with that word length. As is the BESM-6 from the Soviet 
Union, and several computers from the People's Republic of China: the 
Model 109C, the DJS-6 (also known as the Model 108B), the DJS-8 (also 
known as the Model 320), and an early prototype machine based on 
integrated circuits, the Model 013. Photographs of some of those 
computers are visible here; a larger picture of the Model 013 front 
panel appeared in an issue of Datamation magazine.

DJS stands for Dianzi Jisuanji, the Putonghua phrase for "computer" 
(electronic calculator); the Kuo-yü phrase for computer is Tien Nao 
(electric brain) (in Pinyin, Diannao).

Because the Burroughs B5500 and B6700 computers used a word 
containing 48 bits of data, but also extra bits that described the 
type of the data which played an important role in programming the 
machine, I would consider that series sufficiently out-of-the-
ordinary to attempt to discuss here; the same applies to the English 
Electric KDF9 computer, which was stack-oriented like the Burroughs 
machine. The Telefunken TR440 computer also added two descriptor bits 
to each word with 48 bits of data, but these seem to only serve to 
protect the machine against accidentally interpreting instructions as 
data, or integers as floating-point quantities: its instructions were 
24 bits long, with an 8-bit opcode and either a 16-bit address or two 
8-bit indexed addresses, but I have not yet been able to derive the 
structure of an 8-bit address from the available references."



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