PDP-6
Developer | Digital Equipment Corporation |
---|---|
Product family | Programmed Data Processor |
Type | Mainframe computer |
Release date | 1964 |
Operating system | early version of what later became TOPS-10, custom versions of the system, ITS, WAITS |
Platform | DEC 36-bit |
Mass | 1,300 pounds (590 kg), 1,700 pounds (770 kg) with "Fast Memory" |
Successor | PDP-10 |
The PDP-6, short for Programmed Data Processor model 6, is a computer developed by Digital Equipment Corporation (DEC) during 1963 and first delivered in the summer of 1964.[1][a] It was an expansion of DEC's existing 18-bit systems to use a 36-bit data word, which was at that time a common word size for large machines like IBM mainframes. The system was constructed using the same germanium transistor-based System Module layout as DEC's earlier machines, like the PDP-1 and PDP-4.[2]
The system was designed with
The lasting influence of the PDP-6 was its re-implementation using modern
History
DEC's first products were not computers but a series of plug-in circuits known as Digital Laboratory Modules that performed digital logic. Users could wire the modules together to perform specific tasks. DEC soon introduced the PDP-1 which was built out of large numbers of these modules, now known as System Building Blocks or System Modules.[3]
The PDP-1 used an 18-bit word. Word lengths in the early 1960s were generally some multiple of six bits, as the
The PDP-6 was DEC's first "big" machine. It used
Worldwide, only 23 PDP-6's were sold,[6][7] the smallest number of any DEC machine. It was complex and expensive to build, as well as difficult to install and get operational at the customer's site. Additionally, the sales force found the PDP-6 to be a "hard sell". Nevertheless, the company later considered the PDP-6 to be a success:
Because the PDP-6 was the first computer to offer elegant, powerful capabilities at a low price, a great many of the PDP-6s built found their way into university and scientific environments, giving DEC a strong foothold in that market and providing both educated customer input for future models and a source of bright young future employees to assist in the hardware and software development for those future models.[8]
The sales were so slow that DEC eventually decided to abandon the system and announced that they would not build any more 36-bit machines.
Description
Architecture
Addressing remained
The instruction set architecture could be categorized as "one-and-a-half address". The
This left another five bits in the instruction word, bits 13 through 17. Bit 13 indicated the address was indirect; instead of the value stored in address 1234 being added to the selected register, the value in 1234 was interpreted as another address, the value in that location used. For instance, if the value in 1234 is 2345, the resulting instruction would add the value in 2345 to register 4.
The registers in the PDP-6 were simply the first 16 memory locations of main memory. Most, if not all, PDP-6 systems were equipped with the optional Type 162 "Fast Memory", which constructed these 16 memory locations from discrete-transistor flip-flops. These operated four times as fast as the
Hardware
The PDP-6 weighed about 1,300 pounds (590 kg), 1,700 pounds (770 kg) with "Fast Memory".[15]
The PDP-6 was infamous because of the 6205 board, a large (11 × 9 inches) board which contained 1 bit of arithmetic register (AR), memory buffer (MB), and multiplier-quotient register (MQ). The CPU was built from 36 such cards. It had 88 transistors, a two-sided PC etch, two 18-pin and two 22-pin connectors (two on each side of the module). Because of all these connectors, swapping this module was a major undertaking, and the mechanical coupling made it highly likely that fixing one fault would cause another. There was also a great fear of powering off a PDP-6, since it would generally result in at least one 6205 board failing.[16]
The experience with the 6205 led the designers of the first models of PDP-10, the KA10 and KI10, to use only small boards. It was not until the KL10 that large boards were used again.
Operating system
The PDP-6 supported
Although it was possible to time-share a PDP-6 without a disk drive,[17] configuring it with four dual DECtape drives "could effectively support about 4-6 simultaneous users." The same[b] system, with a single[c] disk drive, resulted in "real time-sharing (and) could easily handle 20-30 users."
Museum
Stanford's PDP-6 was shown at DECUS in 1984. The machine was transferred to a DEC warehouse after that event. There are no records of this machine being given to the Computer Museum, which was not part of DEC in 1984. In the late 1990s Compaq donated the contents of the DEC internal archives to The Computer Museum History Center. The Fast Memory cabinet from the Stanford PDP-6 was part of that donation. There is no evidence that the modules sold at the Boston computer museum gift shop were from the Stanford PDP-6, nor is there any evidence that the museum had ever had this machine in its possession.
Notes
References
Citations
- ^ Knight, Tom. "PDP-6 Home Page". MIT CSAIL. Archived from the original on 2 February 2004.
- ^ "A Proposal to American Research and Development Corporation 27 May 1957" (PDF). Retrieved 30 March 2023.
- ^ IBM Corporation (1954). 704 electronic data-processing machine: manual of operation (PDF). p. 35.
- ^ History 1975, pp. 3–5.
- ^ a b History 1975, p. 6.
- ^ "PDP-6". DIGITAL Computing Timeline. Digital Equipment Corporation.
- ^ Bell et al. 1978, p. 487-488.
- ^ Bell et al. 1978, p. 488.
- ^ History 1975, p. 8.
- ^ Larry Lettieri (November 1980). "Foonly challenges DEC patents with emulator". Mini-Micro Systems. pp. 15, 17.
- ^ a b c d Lin & Griffee, p. 2.
- ^ "History". Common Lisp HuperSpec.
The PDP-10 computer and its predecessor the PDP-6 computer were, by design, especially well-suited to Lisp because they had 36-bit words and 18-bit addresses
- ^ Fast Memory Type 162 and Core Memory Type 161C (Technical report). DEC. 1965.
- ^ "PDP-6 documents". www.bitsavers.org. F-68_PDP-6_Installation_Manual_Sep64.pdf, p. 2.
- ^ Lin & Griffee, p. 3.
- ^ DEC Timesharing (1965), by Peter Clark, The DEC Professional (magazine), volume 1, number 1
Bibliography
- Bell, C. Gordon; Kotok, Alan; Hastings, Thomas; Hill, Richard (1978). "The PDP-10 Family" (PDF). Computer Engineering: A DEC View of Hardware Systems Design. DEC.
- DIGITAL EQUIPMENT CORPORATION – Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975.
- Lin, Rick; Griffee, Keegan. "Digital Equipment Corporation PDP-6 & 10" (PDF). University of Washington.
External links
- PDP-6 Serial numbers
- DEC's PDP-6 was the world's first commercial time-sharing system Gordon Bell interview at the Smithsonian
- USENET alt.sys.pdp10 postings comparing the PDP-6 with the KA10
- "PDP-6". DIGITAL Computing Timeline. Digital Equipment Corporation.
- "Tops 10". DIGITAL Computing Timeline. Digital Equipment Corporation.
- "The PDP-6 at Stanford".
- Tom Knight. "The PDP-6 Home Page". Archived from the original on December 9, 2004.