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The Sun Microsystems UltraSPARC processor is a type of RISC microprocessor.. In electronics and computer science, a reduced instruction set computer (RISC) is a computer architecture designed to simplify the individual instructions given to the computer to accomplish tasks.
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
A RISC instruction set normally has a fixed instruction length, whereas a typical CISC instruction set has instructions of widely varying length. However, as RISC computers normally require more and often longer instructions to implement a given task, they inherently make less optimal use of bus bandwidth and cache memories.
RISC-V [b] (pronounced "risk-five" [2]: 1 ) is an open standard instruction set architecture (ISA) based on established reduced instruction set computer (RISC) principles. . The project began in 2010 at the University of California, Berkeley, transferred to the RISC-V Foundation in 2015, and on to RISC-V International, a Swiss non-profit entity, in November 20
Note that in classic RISC, all instructions have the same length. (This is one thing that separates RISC from CISC [1]). In the original RISC designs, the size of an instruction is 4 bytes, so always add 4 to the instruction address, but don't use PC + 4 for the case of a taken branch, jump, or exception (see delayed branches, below).
Before the RISC philosophy became prominent, many computer architects tried to bridge the so-called semantic gap, i.e., to design instruction sets that directly support high-level programming constructs such as procedure calls, loop control, and complex addressing modes, allowing data structure and array accesses to be combined into single instructions.
Building on UC Berkeley RISC and Sun compiler and operating system developments, SPARC architecture was highly adaptable to evolving semiconductor, software, and system technology and user needs. The architecture delivered the highest performance, scalable workstations and servers, for engineering, business, Internet, and cloud computing uses.
This differs from a register–memory architecture (for example, a CISC instruction set architecture such as x86) in which one of the operands for the ADD operation may be in memory, while the other is in a register. [1]: 9–12 The earliest example of a load–store architecture was the CDC 6600.