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Furthermore, an addressing mode which, in one given architecture, is treated as a single addressing mode may represent functionality that, in another architecture, is covered by two or more addressing modes. For example, some complex instruction set computer (CISC) architectures, such as the Digital Equipment Corporation (DEC) VAX, treat ...
However, addressing modes 0–3 were "short immediate" for immediate data of 6 bits or less (the 2 low-order bits of the addressing mode being the 2 high-order bits of the immediate data, when prepended to the remaining 4 bits in that data-addressing byte). Since addressing modes 0-3 were identical, this made 13 (electronic) addressing modes ...
The last two components depend on the addressing mode. For example, on the PDP-11/70 (circa 1975), an instruction of the form ADD x(Rm),y(Rn) had a fetch/execute time of 1.35 microseconds plus source and destination times of 0.6 microseconds each, for a total instruction time of 2.55 microseconds. Any case where addressed memory is not in the ...
For example, the Intel Pentium and the AMD Athlon implement nearly identical versions of the x86 instruction set, but they have radically different internal designs. The concept of an architecture, distinct from the design of a specific machine, was developed by Fred Brooks at IBM during the design phase of System/360.
A complex instruction set computer (CISC / ˈ s ɪ s k /) is a computer architecture in which single instructions can execute several low-level operations (such as a load from memory, an arithmetic operation, and a memory store) or are capable of multi-step operations or addressing modes within single instructions.
The design of the CPU allows RISC computers few simple addressing modes [2] and predictable instruction times that simplify design of the system as a whole. The conceptual developments of the RISC computer architecture began with the IBM 801 project in the late 1970s, but these were not immediately put into use.
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The SIC machine has basic addressing, storing most memory addresses in hexadecimal integer format. Similar to most modern computing systems, the SIC architecture stores all data in binary and uses the two's complement to represent negative values at the machine level.