PDP-8
PDP-8 (Programmable Data Processor) is the programmable processor of data. The family of minicomputers developed by DEC corporation (Digital Equipment Corporation). Some are inclined to consider PDP-8 the first minicomputer, however it is not absolutely right if to consider that before seven more versions of PDP were collected. The first model is provided to the public on March 22, 1965. PDP-8 system had the mass of similar solutions clones worldwide. In the USSR, in particular, there were several analogs of this computer: Electronics-100, Electronics-100I and also Saratov-2.
Specifications
The machine had the 12-bit processor and the 12-bit data bus. RAM in 4 Kb, with an opportunity to expand to 48 Kb. Speed of storage access was 1.2 microsec. Power consumption from 450 watts, there could be more depending on a configuration. This family was one of the most popular in the world. The price of a basic complete set — 18 thousand USD. Only the microcomputer of Apple II could exceed PDP-8 by the number of sales.
The bus PDP-8 allowed to connect up to 20 external devices. The machine could execute 380 thousand addition operations of 12-bit numbers and 340 thousand division operations per second. It has very developed command system. Which are divided into three groups. Commands which work with operands in RAM belong to the first group. Auxiliary commands and the servicing commands. The commands working with operands have the following format. The first three bits are an activity code, the following two bits define an addressing mode and the last contain the address or data. Auxiliary commands are separated into two groups: instructions of input-output, functional instructions.
All peripheral devices are separated as connection to the mini computer. The first are connected not indifferently to the data bus, the second via interfaces. The bus consists 144 channels. The last three bits of a command transferred determine all operation by this bus.
The software and development tools for PDP-8 was extensive. Except the macroassembler also languages of the high level were applied: FORTRAN, COBOL, BASIC. There were many debuggers and special utilities.
Interesting Facts
PDP-8 gathered completely automatically, but not as her predecessors for a half manually. This fact allowed to adjust the release of serial commercial minicomputers first in the history. From the PDP series the eighth model was the cheapest on production.
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