Search results
Results from the WOW.Com Content Network
Minimal instruction set computer (MISC) is a central processing unit (CPU) architecture, usually in the form of a microprocessor, with a very small number of basic operations and corresponding opcodes, together forming an instruction set. Such sets are commonly stack-based rather than register-based to reduce the size of operand specifiers.
The types of operations may include arithmetic, data copying, logical operations, and program control, as well as special instructions (e.g., CPUID). [10] In addition to the opcode, many instructions also specify the data (known as operands) the operation will act upon, although some instructions may have implicit operands or none at all. [10]
The MIPS architecture provides a specific example for a machine code whose instructions are always 32 bits long. [5]: 299 The general type of instruction is given by the op (operation) field, the highest 6 bits. J-type (jump) and I-type (immediate) instructions are fully specified by op.
(In the examples that follow, a, b, and c are (direct or calculated) addresses referring to memory cells, while reg1 and so on refer to machine registers.) C = A+B 0-operand (zero-address machines), so called stack machines: All arithmetic operations take place using the top one or two positions on the stack: [9] push a, push b, add, pop c.
In synchronous operation, characters must be provided on time until a frame is complete; if the controlling processor does not do so, this is an "underrun error," and transmission of the frame is aborted. USARTs operating as synchronous devices used either character-oriented or bit-oriented mode.
A high-level illustration showing the decomposition of machine instructions into micro-operations, performed during typical fetch-decode-execute cycles [1]: 11 . In computer central processing units, micro-operations (also known as micro-ops or μops, historically also as micro-actions [2]) are detailed low-level instructions used in some designs to implement complex machine instructions ...
PMIO was very useful for early microprocessors with small address spaces, since the valuable resource was not consumed by the I/O devices. The best known example of a PC device that uses programmed I/O is the Parallel AT Attachment (PATA) interface; however, the AT Attachment interface can also be operated in any of several DMA modes.
In simpler CPUs, the instruction cycle is executed sequentially, each instruction being processed before the next one is started. In most modern CPUs, the instruction cycles are instead executed concurrently, and often in parallel, through an instruction pipeline: the next instruction starts being processed before the previous instruction has finished, which is possible because the cycle is ...