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Lecture 1: introduction to Hardware Architecture

Hierarchy of Computer Architecture

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Hardware Architecture

The First Computer

• ENIAC (Electronic Numerical Integrator And Calculator) • Developed at the University of Pennsylvania • Funded by the US Department of Defense • It became operational during the II world war • Built between 1943 and 1946 • Made public in 1946 • The designers were J.P. Eckert and J. Mauchly

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ENIAC

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ENIAC

• General purpose machine used for the calculation of artillery shooting tables • A "U" of 30 meters high 2m and 1m thick • 30 tons • 18,000 vacuum tubes (valves) • 20 10-digit registers (each register over half a meter) • 200 microsecs for an addition • 180 KW of consumption. When it was put into operation for the first time, the entire west district of Philadelphia went in black-out. • Manual programming through wires and switches • Data introduced through punched cards • Tedious and error-prone to program

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The Von Neumann Architecture

• John Von Neumann was part of the ENIAC group

• He wrote a memo based on ENIAC, proposing a computer called EDVAC (Electronic Discrete Variable Automatic Computer)

• Turned to history, even if the ideas were of others

• Key feature: stored program (in the central memo)

• All computers are based on this model, now universally known as the Von Neuman Machine

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The Von Neumann Architecture

• This model is based on the following fundamental observations:

• the computer must perform arithmetic operations more frequently, so it is reasonable that it has one or more specialized devices for such operations • the logical control of the device, i.e. the correct sequence with which to perform such operations, can be carried out more efficiently by a flexible central controller, which distinguishes between order of execution of the instructions (they depend on the problem to be solved, so they must be stored) and modalities of execution of the single instructions (they depend on the calculator, for which they are managed by the device itself) • the sequence of instructions and the data on which it operates must be stored in memory • data and results must be able to be exchanged with the outside through input / output units (input / output) • all the devices mentioned must be able to talk to each other through appropriate connections

• Let's see briefly the resulting model

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The Von Neumann Architecture

Executes the Connection/ instructions Communication

(Central Processing Unit) Working Memory bus

Hardware: the Von Neumann Architecture

CPU (Central Processing Unit) is the brain of the computer, as it coordinates and manages all the (Central Processing Unit) various hardware devices for program execution. It is bus composed by:

The control unit (CU) deals with the interpretation and execution of instructions. It is the component of a computer's CPU that directs the operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and output devices how to respond to the instructions that have been sent to the processor.

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Hardware: the Von Neumann Architecture

An Arithmetic Logic Unit (ALU) that is a (Central Processing Unit) combinational digital electronic circuit that performs arithmetic and bitwise operations on integer binary bus numbers. An ALU is a fundamental building block of many types of computing circuits, including the CPU of computers, FPUs, and graphics processing units (GPUs). A single CPU, FPU or GPU may contain multiple ALUs.

Several Registers - A processor register is a quickly accessible location available to a computer's CPU. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write- only. An example of register is the Program Counter.

Hardware: the Von Neumann Architecture

(Central Processing Unit)

bus A clock that scans the time intervals in which the devices inside the C.P.U. It determines the speed of the C.P.U., expressed as the frequency or number of intervals scanned in the unit of time (eg, 512MHz, 1GHz, 2GHz ...)

Some examples of CPU: Intel® Core ™ I7, AMD® Phenom II,

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CPU state Logic and CPU Address of the next Flag: C, Z, S, O Arithmetic instruction operations

Status registry (PSW) Program Counter (PC) A Interrupt Registry ALU (INTR) B Operands Registries Instruction Registry (IR) Other Registries

Instruction in execution Control Unit Clock (CU) Control: Synchronization -Fetch -decode Data Registry Addresses Registry (DTR) (MAR) -execute

Word to read from or write in the Memory Memory address to access 13

Hardware: the Von Neumann Architecture Random-access memory (RAM) is a form of computer data storage that stores data and machine (Central Processing Unit) code currently being used. A random-access memory device allows data items to be read or written in bus almost the same amount of time irrespective of the physical location of data inside the memory.

It stores the instructions (in machine language) that must be performed and the data on which they operate. It has the characteristic of being: volatile: its contents are lost when the computer is turned off fast (nanosecond order, ie 10-9 seconds) expensive medium-small size, from a few hundred megabytes (eg 512MB in mobile devices) to a few gigabytes (desktop and server machines)

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RAM Volatile h bit word Data and instructions 0 1

Address Registry (MAR) Data Registry (DTR) store

k bit load h bit

Cell Address Data to read or write

2k-1 Space of addressing 2k cells 15

Hardware: the Von Neumann Architecture

The input/output controller (alternatively referred to (Central Processing Unit) as an input/output interface, IOC, or PIOC for bus Peripheral input/output controller) is a device that interfaces between an input or output device and the computer or hardware device. The input/output controller on a computer is commonly located on the motherboard.

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I/O Device: Mass Memory • Although it is a key component, it is not part of the Von Neumann machine in the strict sense (Central Processing Unit) • It consists of hard disks, tapes, CDs and DVD ROMs, ... bus • Compared to the central memory it has the characteristic of being • non-volatile • slow (for hard disk order of milliseconds, i.e., 10-3 seconds) • economic • large (for hard drives hundreds of gigabytes, a few terabytes)

• In contrast to RAM, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement. 17

I/O Device

(Central Processing Unit) • They allow the communication of the bus computer with the outside and in particular the reading of data in input and the return of the results of the elaborations in output.

• These include terminals (keyboard and screen), mice, printers, scanners, ...

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System Bus

(Central Processing Unit) • Allows communication between the various bus components

• It is subdivided into • Data bus: for data transmission • Address bus: for the transmission of central memory addresses • Control bus: for the transmission of commands to the various units and control information

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