Computer architectures

There are many types of computer architectures:

• Quantum computer vs Chemical computer
• Scalar processor vs Vector processor
• Non-Uniform Memory Access (NUMA) computers
• Register machine vs Stack machine
• Harvard architecture vs von Neumann architecture
• Cellular architecture

The quantum computer architecture holds the most promise to revolutionize computing.^[4]

[edit] Computer architecture topics

[edit] Sub-definitions

Some practitioners of computer architecture at companies such as Intel and AMD use more fine distinctions:

• Macroarchitecture — architectural layers that are more abstract than microarchitecture, e.g. ISA
• Instruction Set Architecture (ISA) — as defined above
• Assembly ISA — a smart assembler may convert an abstract assembly language common to a group of machines into slightly different machine language for different implementations
• Programmer Visible Macroarchitecture — higher level language tools such as compilers may define a consistent interface or contract to programmers using them, abstracting differences between underlying ISA, UISA, and microarchitectures. E.g. the C, C++, or Java standards define different Programmer Visible Macroarchitecture — although in practice the C microarchitecture for a particular computer includes
• UISA (Microcode Instruction Set Architecture) — a family of machines with different hardware level microarchitectures may share a common microcode architecture, and hence a UISA.
• Pin Architecture — the set of functions that a microprocessor is expected to provide, from the point of view of a hardware platform. E.g. the x86 A20M, FERR/IGNNE or FLUSH pins, and the messages that the processor is expected to emit after completing a cache invalidation so that external caches can be invalidated. Pin architecture functions are more flexible than ISA functions - external hardware can adapt to changing encodings, or changing from a pin to a message - but the functions are expected to be provided in successive implementations even if the manner of encoding them changes.

[edit] The Role Of Computer Architecture

[edit] Computer Architecture: The Definition

The coordination of abstract levels of a processor under changing forces, involving design, measurement and evaluation. It also includes the overall fundamental working principle of the internal logical structure of a computer system.
It can also be defined as the design of the task-performing part of computers, i.e how various gates and transistors are interconnected and are caused to function per the instructions given by an assembly language programmer.

[edit] Instruction Set Architecture

1. The ISA is the interface between the software and hardware.
2. It is the set of instructions that bridges the gap between high level languages and the hardware.
3. For a processor to understand a command, it should be in binary and not in High Level Language. The ISA encodes these values.
4. The ISA also defines the items in the computer that are available to a programmer. For example, it defines data types, registers, addressing modes, memory organization etc.
5. Register are high speed storage for numbers that can be accessed by a processor. Data as well as instructions can be in a register.

Addressing modes are the ways in which the instructions locate their operands.
Memory organization defines how instructions interact with the memory.