PDP-11 was a series of 16-bit minicomputers manufactured by Digital Equipment Corp. in the 1970s and 1980s. It pioneered the interconnection of all system elements\u2014processor, RAM, and peripherals\u2014to a single, bidirectional, asynchronous communication bus. This device, called Unibus, allowed devices to send, receive, or exchange data without the need for an intermediate memory pass. The PDP-11 series was one of the best-selling minicomputer series of its time and one of the first to run the Unix OS, developed at Bell Labs.<\/p>\n
The series has evolved with the advancement of technology, going from a CPU consisting of TTL MSI integrated circuits to microprocessors such as the LSI-11. The latest versions, from PDP-11\/75 onwards, incorporated the J-11, with duplicate registers, three stacks (User, Core and Supervisor), virtual memory (22 bits), cache and separate memory spaces for instructions and data. It was a very ambitious chip for the time, but it never quite lived up to expectations, due to design issues and discussions between DEC and Harris Semiconductor, the chip maker.<\/p>\n
During the Cold War, the architecture of the PDP-11 series was cloned in the USSR without authorization from the manufacturer. In this way, programs developed for the series could run smoothly on the Soviet clones.<\/p>\n\n\n