1965 DEC PDP-8
The 12-bit PDP-8 machine was the first commercially successful (for it was) minicomputer, produced by Digital Equipment Corporation (DEC) in the 1960s. DEC introduced it on March 22, 1965, and it sold over 50,000 systems, plus than any computer to date.[1] It was the first widely sold computer of DEC’s series of computers (the PDP-5 was not originally intended to be a general-purpose computer).
The older model PDP-8 (known informally as the “Straight-8”), used “Diode-transistor logic” diodes, packaged in Flip Chip boards, and was the size of a mini-fridge.
This was followed by the PDP-8/S, a desktop model. Using a one-bit serial ALU implementation, the PDP-8/S was smaller, less expensive, but much slower than the original PDP-8.
Later systems (the PDP-8/I and /L, the PDP-8/E, F, and /M, and PDP-8/A) returned to a faster, fully parallel implementation but used cheaper TTL logic. and MSI integrated circuits. Most surviving PDP-8s are from this era. The PDP-8/E is common and well-regarded because many types of I/O devices were available for it. It was often configured as a general purpose computer.
In 1975, the first low-cost microprocessor-based personal computers, such as the MITS Altair and later the Apple II, began to dominate the small general-purpose computer market.
The last commercial models of the PDP-8 in 1979 were called “CMOS-8” and used custom CMOS microprocessors. They were not competitively priced, and supply failed to meet demand. The IBM PC, in 1981, cemented the condemnation of the CMOS-8s, making a legitimate and well-supported computer with small microprocessors.
he PDP-8 was the first sucessful commercial minicomputer, produced by DEC in the 60s, the first real minicomputer, and the first computer costing less than $20,000.
By late 1973 to 77, the PDP-8 family was the best selling computer in the world. The basic version could sit on a desktop rather than requiring cumbersome racks well known at the time. This compact size caused it to become a popular system in scientific laboratories.
The machine had a now quite strange 12-bit word and four thousand 12-bit words of magnetic core memory. The first model was built without any Integrated circuit – thus no microprocessor – but with discrete transistors mounted on numerous small printed circuit boards called ‘flip chips’ that were inserted on two backplanes mounted vertically. Both table-top and rack-mount models were available, but adding additional memory required a rack.
CPU was composed of 12 interlinked Register Boards each operating on one bit slice of the 12 bit word and containing an Adder function together with all the major registers – MB, MA, AC, PC. Speed a little less than 1MHz.
The instructions set of the PDP-8 was very limited, only eight basic instructions encoded by the three left bits of each 12-bit word, and one register, the accumulator: However, the PDP-8 could be programmed to do almost anything. It just took longer (sometimes very longer!) to execute programs.
A 110 baud current loop teletype interface allowed an ASR 33 Teletype to be connected, serving as a console as well as a storage device by means of the built-in papertape puncher and reader.
There were numerous variations of the original model over the years, among them:
1966: PDP-8/S – minimum price but slow memory serial logic design
1968: PDP-8/I – first version with integrated circuits
1970: PDP-8/E – New bus structure design called Omnibus
1975: PDP-8/A – Allowed OEMs choice of memory type and quantity
All together, about 50,000 PDP-8 series computers were sold, as well as numerous clones made USA, Asia and East European countries.
In 2000 year, there were still a few PDP8’s in operation, mainly in third-world countries.
| NAME | PDP-8 |
| MANUFACTURER | Digital Equipment Corporation |
| TYPE | Professional Computer |
| ORIGIN | U.S.A. |
| YEAR | 1965 |
| END OF PRODUCTION | 1980 |
| BUILT IN LANGUAGE | None |
| KEYBOARD | ASR-33 Teletype |
| CPU | CPU was composed of 12 interlinked Register Boards |
| SPEED | 1 MHz (0.5 MIPS) |
| RAM | 4 K of 12 bit words |
| TEXT MODES | Depending of the terminal used |
| SIZE / WEIGHT | 48 (W) x 55 (D) x 84 (H) cm. / 150 Kgs. |
| I/O PORTS | 110 Baud serial interface |
| BUILT IN MEDIA | None |
| POWER SUPPLY | Built-in 780 Watts power supply unit |
| PERIPHERALS | Memory boards up to 32 Kwords |
| PRICE | $18.000 (Basic version) |
A modern PDP-8 replica using Raspberry PI is available at PDP-8
Related
Filed under: Honorable Mentions - @ January 31, 2022 10:47 AM