PDP-11

The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, making it one of DEC's most successful product lines. The PDP-11 is considered by some experts to be the most popular minicomputer.

The PDP-11 included a number of innovative features in its instruction set and additional general-purpose registers that made it much easier to program than earlier models in the PDP series. Additionally, the innovative Unibus system allowed external devices to be easily interfaced to the system using direct memory access, opening the system to a wide variety of peripherals.

The design of the PDP-11 inspired the design of late-1970s microprocessors including the Intel x86 and the Motorola 68000. The design features of PDP-11 operating systems, and other operating systems from Digital Equipment, influenced the design of operating systems such as CP/M and hence also MS-DOS. The first officially named version of Unix ran on the PDP-11/20 in 1970. It is commonly stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not originally by design.

An effort to expand the PDP-11 from 16 to 32-bit addressing led to the VAX-11 design, which took part of its name from the PDP-11.

The PDP-11 processor architecture has a mostly orthogonal instruction set. For example, instead of instructions such as load and store, the PDP-11 has a move instruction for which either operand (source and destination) can be memory or register. There are no specific input or output instructions; the PDP-11 uses memory-mapped I/O and so the same move instruction is used; orthogonality even enables moving data directly from an input device to an output device. More complex instructions such as add likewise can have memory, register, input, or output as source or destination.

For a decade, the PDP-11 was the smallest system that could run Unix, but in the 1980s, the IBM PC and its clones largely took over the small computer market; BYTE in 1984 reported that the PC's Intel 8088 microprocessor outperformed the PDP-11/23 when running Unix. Newer microprocessors such as the Motorola 68000 (1979) and Intel 80386 (1985) also included 32-bit logical addressing.

 六级/考研单词: digit, equip, data, expertise, innovate, instruct, inspire, destination, likewise, clone, compute, logic

The Development of the C Language (bell-labs.com) 

Great Microprocessors of the Past and Present (V 13.4.0) (cpushack.com)

Part VI: MIL-STD-1750 - Military artificial intelligence (February 1979) .
The USAF created a draft standard for a 16-bit microprocessor meant to be used in all airborn computers and weapons systems, allowing software developed for one such system to be portable to other similar applications, similar to the intent behind the creation of Ada as the standard high level programming language for the U.S Department of Defense (MIL-STD-1815 accepted October 1979 - 1815 was the year Ada Augusta, Countess of Lovelace and the world's first programmer, was born)...

The 8087 was a floating point coprocessor which helped define the IEEE-754 floating point format and standard operations (the main competition was the VAX floating point format), and was based on an eight element stack of 80-bit values. An instruction prefix (0xE0) indicated coprocessor instructions (similar to the 68000), so the coprocessor could "listen" to the instruction stream, and execute instructions it recognized, without a coprocessor bus.

The 80486 (1989) added full pipelines, single on chip 8K cache, FPU on-chip, and clock doubling versions (like the Z-280). Later, FPU-less 80486SX versions plus 80487 FPUs were introduced - initially these were normal 80486es where one unit or the other had failed testing, but versions with only one unit were produced later (smaller dies and reduced testing reduced costs).

The Pentium (late 1993) was superscalar (up to two instructions at once in dual integer units and single FPU) with separate 8K I/D caches.

MMX (initially reported as MultiMedia eXtension, but later said by Intel to mean Matrix Math eXtension) is very similar to the earlier SPARC VIS or HP-PA MAX, or later MIPS MDMX instructions - they perform integer operations on vectors of 8, 16, or 32 bit words, using the 80 bit FPU stack elements as eight 64 bit registers (switching between FPU and MMX modes as needed - it's very difficult to use them as a stack and as MMX registers at the same time).

IBM had been developing hardware or software to translate Pentium instructions for the PowerPC in a similar manner as part of the PowerPC 615 CPU (able to switch between instruction 80x86, 32-bit and 64-bit PowerPC instruction sets in five cycles (to drain the execution pipeline)), but the project was killed after significant development for marketing reasons. Rumour has it that engineers who worked on the project went on to Transmeta corporation.

A server (Xeon) version of the P7 (March 2002) introduced vertical multithreading (called "Hyperthreading" by Intel), similar to the IBM Northstar CPU (or Sun MAJC)

AMD aggressively pursued a superscalar (fourteen-stage pipeline) design for the Athlon (K7, mid 1999),

Intel, with partner Hewlett-Packard, developed a next generation 64-bit processor architecture called IA-64 (the 80x86 design was renamed IA-32) - the first implementation was named Itanium. [某总部设在西北旺东路的国际公司紧跟了这个CPU]

When moving from the 80286 to the 80386 (IA-32), Intel took the opportunity to fix some of the least liked features remaining in the previous design. Moving to x86-64, AMD decided to further modernize the design, adding a cleaner 64-bit mode (selected by Code Segment Descriptor (CSD) register bits).

Rumours persisted that Intel was developing a CPU codenamed "Yamhill", originally based on original 64-bit P7 plans dusted off, but then switching to the x86-64 architecture and instruction set (apparently under pressure from Microsoft to avoid creating yet another instruction set to support - ironically making Intel a follower of AMD, after driving 80x86 development from the beginning).