DECsystem-10

DEC PDP-10 registers

00 . . . 17 18 . . . 35 (bit position) General registers   AC0 Register 0   AC1 Register 1   AC2 Register 2   AC3 Register 3   AC4 Register 4   AC5 Register 5   AC6 Register 6   AC7 Register 7   AC10 Register 8   AC11 Register 9   AC12 Register 10   AC13 Register 11   AC14 Register 12   AC15 Register 13   AC16 Register 14   AC17 Register 15 Program counter and status flags Program Flags 00000 PC Program Counter Note that the bit numbering order is different from some other DEC processors, and many newer processors.

The PDP-10 is a discontinued mainframe computer family manufactured by Digital Equipment Corporation (DEC) from 1966 into the 1980s.

The PDP-10 architecture is almost identical to the earlier PDP-6 architecture, sharing the same 36-bit word length and slightly extending the instruction set (but with improved hardware implementation). Some aspects of the instruction set are unusual, most notably the "byte" instructions, which operated on bit fields of any size from 1 to 36 bits inclusive according to the general definition of a byte as a contiguous sequence of a fixed number of bits.

The PDP-10 is the machine that made time-sharing common, and this and other features made it a common fixture in many university computing facilities and research labs during the 1970s, the most notable being Harvard's Aiken Lab,MIT's AI Lab and Project MAC, Stanford's SAIL, Computer Center Corporation (CCC), ETH (ZIR), and Carnegie Mellon University. Its main operating systems, TOPS-10 and TENEX, were used to build out the early ARPANET. For these reasons, the PDP-10 looms large in early hacker folklore.

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