ZISC

A Complex Instruction Set Core (CISC) is a microprocessor instruction set architecture (ISA) in which each instruction can execute several low-level operations, such as a load from memory, an arithmetic operation, and a memory store, all in a single instruction. The term was coined in contrast to Reduced Instruction Set Computer (RISC). Before the first RISC processors were designed, many computer architects tried to bridge the "semantic gap" - to design instruction sets to support high-level programming languages by providing ...

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While the RISC philosophy was coming into its own, new ideas about how to dramatically increase performance of the CPUs were starting to develop. In the early 1980s it was thought that existing design was reaching theoretical limits. Future improvements in speed would be primarily through improved semiconductor "process", that is, smaller features (transistors and wires) on the chip. The complexity of the chip would remain largely the same, but the smaller size would allow it to run at higher clock rates. A considerable amount of effo ...

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RISC, RISC - RISC design philosophy, RISC - Pre-RISC design philosophy, RISC - Meanwhile..., RISC - Early RISC, RISC - Later RISC, RISC - Alternative term

Read more here: » RISC: Encyclopedia II - RISC - Meanwhile...

Berkeley's research was not directly commercialized, but the RISC-II design was used by Sun Microsystems to develop the SPARC, by Pyramid Technology to develop their line of mid-range multi-processor machines, and by almost every other company a few years later. It was Sun's use of a RISC chip in their new machines that demonstrated that RISC's benefits were real, and their machines quickly outpaced the competition and essentially took ...

See also:

RISC, RISC - RISC design philosophy, RISC - Pre-RISC design philosophy, RISC - Meanwhile..., RISC - Early RISC, RISC - Later RISC, RISC - Alternative term

Read more here: » RISC: Encyclopedia II - RISC - Later RISC

The first system that would today be known as RISC was not at the time; it was the CDC 6600 supercomputer, designed in 1964 by Jim Thornton and Seymour Cray. Thornton and Cray designed it as a number-crunching CPU (with 74 op-codes, compared with a 8086's 400) plus 12 simple computers called "peripheral processors" to handle I/O (most of the operating system was in one of these). The CDC 6600 had a load/store architecture with only two addressing modes. There were eleven pipelined functional units for arithmetic and logic, plus five load uni ...

See also:

RISC, RISC - RISC design philosophy, RISC - Pre-RISC design philosophy, RISC - Meanwhile..., RISC - Early RISC, RISC - Later RISC, RISC - Alternative term

Read more here: » RISC: Encyclopedia II - RISC - Early RISC

In the early days of the computer industry, compiler technology did not exist. Programming was done in either machine code or assembly language. To make programming easier, computer architects created more and more complex instructions which were direct representations of high level functions of high level programming languages. The attitude at the time was that hardware design was easier than compile ...

See also:

RISC, RISC - RISC design philosophy, RISC - Pre-RISC design philosophy, RISC - Meanwhile..., RISC - Early RISC, RISC - Later RISC, RISC - Alternative term

Read more here: » RISC: Encyclopedia II - RISC - Pre-RISC design philosophy

In the late 1970s research at IBM (and similar projects elsewhere) demonstrated that the majority of these "orthogonal" addressing modes were ignored by most programs. This was a side effect of the increasing use of compilers to generate the programs, as opposed to writing them in assembly language. The compilers in use at the time only had a limited ability to take advantage of the features provided by CISC CPUs; this was largely a result of the difficulty of writing a compiler. The market was clearly moving to even wider use of compilers, diluting the ...

See also:

RISC, RISC - RISC design philosophy, RISC - Pre-RISC design philosophy, RISC - Meanwhile..., RISC - Early RISC, RISC - Later RISC, RISC - Alternative term

Read more here: » RISC: Encyclopedia II - RISC - RISC design philosophy