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Microarchitecture, abbreviated as µarch or uarch, is the fundamental design of a microprocessor. It includes the technologies used, resources and the methods by which the processor is physically designed in order to execute a specific instruction set (ISA or instruction set architecture). Simply put, it is the logical design of all electronic components and data paths present in the microprocessor, laid out in a specific way that it allows for optimal execution of instructions. In academe this is called computer organization.
Microarchitecture is the logical representation of how a microprocessor is designed so that the interconnections between components – the control unit, the arithmetic logic unit, registers and others – interact in an optimized manner. This includes how buses, the data pathways between components, are laid out to dictate the shortest paths and proper connections. In modern microprocessors there are often several layers to deal with complexity. The basic idea is to lay out a circuit that could execute commands and operations that are defined in an instruction set.
A technique that is currently used in microarchitecture is the pipelined datapath. It is a technique that allows a form of parallelism that is applied in data processing by allowing several instructions to overlap in execution. This is done by having multiple execution pipelines that run in parallel or close to parallel.
Execution units are also a crucial aspect of microarchitecture. Execution units perform the operations or calculations of the processor. The choice of the number of execution units, their latency and throughput is a central microarchitectural design consideration. The size, latency, throughput and connectivity of memories within the system are also microarchitectural decisions.
Another part of a microarchitecture is system-level design. This includes decisions on performance such as level and connectivity of input, as well as output and I/O devices.
Microarchitectural design pays closer attention to restrictions than capability. A microarchitecture design decision directly affects what goes into a system; it heeds to issues such as:
A good microarchitecture is one that caters to all of these criteria.