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CASINO (an acronym for 'Computer Able to Select INternal Orders') was an early, one-of-a-kind computer built out of DEC System Modules by Scientific Engineering Institute (which later became Medidata; they were eventually bought by G.D. Searle & Co., and re-named Searle Medidata).

It was based on the specification (which included an ISA) for the never-produced PDP-3, but the design (performed at SEI, according to later memories) was modified in the course of bringing the machine up. It apparently used 36-bit words (from the width of the main memory known to have been used on it; below), but this is not certain. It initially used a loop of magnetic tape for secondary storage, but that was later replaced by a drum.

SEI initially used it "to process radar cross section data for the Lockheed A-12 reconnaissance aircraft in 1960". It is possible that it was also used for running theoretical models related to RCS work, but that is a guess (based in part on the need for secondary storage). The last use that CASINO was put to at SEI, before being retired ("the board testing function now being carried out on CASINO", below) was almost certainly a re-use of a machine they had laying around.

CASINO was also reported to have had graphics capabilities, at a time when that was very rare.


A few brief references to CASINO remain:

From Gordon Bell's book Computer Engineering - A DEC View of Hardware Systems Design:

DEC also never built a PDP-3, although one was designed on paper as a 36-bit machine. [...] In 1960 a customer (Scientific Engineering Institute, Waltham, Massachusetts) built a PDP-3. It was later dismantled and given to M.I.T.: as of 1974, it was up and running in Oregon.

From From RAINBOW to GUSTO: Stealth and the Design of the Lockheed Blackbird:

As the amount of radar testing at the Ranch increased, the scientists at SEI decided that the data had become too much to process by hand. To speed things up, they decided that a computer would be needed. The difficulty was that no computer within their budget was available off the shelf. So they decided to build their own.
In October 1960, the Digital Equipment Corporation (DEC) had produced a specification for the PDP-3, a new system in their line of programmable data processor minicomputers. Ed Rawson took charge of the project and with the help of Chuck Corderman and Jay Lawson designed and built a PDP-3 using standard DEC logic modules. [EG&G personnel sometimes teased Rawson that the SEI folks must have held stock in DEC.] Because disk drives were not available, a tape loop running through an Ampex tape drive held intermediate results; eventually, the tape loop was replaced with a drum memory. The project was run like a homebrew computer project, with more emphasis on getting the machine and software to run rather than on making it well documented and easy to use. The design evolved so rapidly that when one of the engineers returned after a two-week absence, he didn’t recognize it. The design evolved away from the original PDP-3 architecture, and it came to be called CASINO ...
Eventually the system worked. Radar data were recorded by EG&G at the Ranch on 1-in.-wide data tapes and shipped to SEI ... The data could be processed correctly, but the computer could usually only be operated with Rawson looking over the user’s shoulder. Eventually the PDP-3 was discarded; one computer engineering textbook stated that in the early 1980s it was running somewhere in Washington state, but the author of that book could not confirm it ... There is an unconfirmed report that it was donated to a Boy Scout troop and eventually given to Dow Chemical for disposal. It was the only example of a PDP-3 ever built.

From a September 21, 1972 letter from Edward B. Rawson:

As you may have heard, we have been considering the question of what to do with our CASINO computer. The machine is nearing the end of its useful life. We have recently purchased a General Radio 1792 to supply the board testing function now being carried out on CASINO. I anticipate that within six to nine months we will have no further use for CASINO. [...]
The machine contains primarily 1000, 4000 and 6000 series systems units. Many of the 6000 series units have been modified or had selected transistors placed in them. In general, the modifications are minor. The units are, of course, largely in working order although unused portions of the units may have failed during the life of the machine without our noticing the failures. Most of the equipment racks are of the taper pin variety. However, in addition, there are perhaps twenty racks of the banana plug type. The relay racks are not standard DEC hardware; they were purchased from EMCOR.
In addition to the systems units and racks, the machine contains a couple of major components of DEC manufacture. One of these is a type 30 scope which may have been modified but probably not drastically. A second item is the basic 4K memory. This memory consists of two PDP-1 memories placed on top of one another to provide 38-bit words. The stacks and drivers could conceivably be quite useful to you. The entire stacked up memory array was manufactured by Digital Equipment in 1960. The bulk of the memory in the machine is a 16K Fabri-tek memory of 40-bit word length. I am presuming that this memory will be of no interest to DEC.
In addition to these items, there are several other peripherals which may or may not be of interest. These include three Potter tape transports, one of which has Potter electronics. The other two of these units contain SMI constructed read and write electronics. We have a couple of used but still useful Friden Flexowriters, some paper tape equipment which I am sure is not of interest to DEC, and a Cal-Comp plotter.

From a February 3, 1997 alt.sys.pdp10 message from Max ben-Aaron:

In the late 60's & early 70's I worked for a company (Medidata, later Searle Medidata) which started life as a not-for-profit spin-off from Lincoln Lab. (as I have heard), called American Science Institute. The chief engineer, Ed Rawson was a friend of Dec's Olsen and he managed to get hold of the modules used for the prototype PDP-2 which never reached the market. ASI used them to build their own machine (designed, I believe, by Chuck Corderman) which they called "Casino" and was sometimes jocularly referred to as a PDP-2 1/2. Casino was noteworthy for having, very early in the game, graphics capabilities. It also had some special terminals which had labels that cannot be repeated on this (family) newsgroup.

(His memory seems to have dropped a bit or two; Medidata was previously 'Scientific Engineering Institute', not "American Science Institute". Also, the modules he speaks of were almost certainly not PDP-2-specific modules, but just generic DEC System Modules (per the Rawson letter).)