|
The PDP-6 (''Programmed Data Processor-6'') was a computer model developed by Digital Equipment Corporation (DEC) in 1963. It was influential primarily as the prototype (effectively) for the later PDP-10; the instruction sets of the two machines are almost identical. ==Architecture== The PDP-6 was DEC's first "big" machine. It used 36-bit words, in common with other large computers at the time from companies like IBM, Honeywell and General Electric. Addressing remained 18-bit, as in earlier DEC machines, allowing for a 256 kword main memory. Memory was implemented using magnetic cores; a typical system included 32,768 words (equivalent to 144kB on modern machines). The instruction set architecture could be categorized as "one-and-a-half address"; instructions contained one full 18-bit memory address, and a second four-bit address that could specify one of the first sixteen memory locations as an "accumulator" or "AC". Another four-bit field in the instruction allowed for any AC other than AC0 to be used as an index register. Most, if not all, PDP-6 systems were equipped with the optional Type 162 "Fast Memory", which provided 16 memory locations constructed from discrete-transistor flip-flops. The Fast Memory (also known as "fast accumulators" or "fast ACs") substituted for the first 16 words of core memory and operated four times faster. The PDP-6 supported time sharing through the use of a status bit selecting between two operating modes ("Executive" and "User", with access to I/O, etc., being restricted in the latter), and a single relocation/protection register which allowed a user's address space to be limited to a set section of main memory (a second relocation/protection register for shareable "high segments" was added on the PDP-10). The main operating system used on the machine was an early version of what later became TOPS-10, and several sites made custom versions of the system, which was available in source code form. MIT's ITS operating system also began on the PDP-6. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「PDP-6」の詳細全文を読む スポンサード リンク
|