1

Inside the

Personal Computer

Department of Computer Science

Faculty of Civil Engineering, Brno University of Technology

Information Technology 1

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Repetition

• A computer is a data processing machine which isoperated automatically under the control of a listof instructions (called a program) stored in itsmain memory.

• Conventional digital computers have a common formthat is attributed to von Neumann.

• Von Neumann computers are general purposecomputers.

• Data and instructions are both storedin the main memory.

• Central processing unit (CPU, processor) contains thecontrol unit that coordinates the execution of instructions, and the arithmetic-logic unit that performs arithmetic and logic operations.

3

Repetition

Control unitArithmetic-logic

unit

Registers

Main memory(operational)

CPU

Instructions Data

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Repetition

• The main (operational) memory is used to storeprogram and data which are currently manipulatedby the CPU. Main memory is fast and of limited size.

• The peripheral (secondary) memory provides thelong-term storage of large amounts of data and program. It is relatively slow and of very large size.

• The most important characteristics of a memory arespeed (access time and data transfer rate), size and cost, which are mainly constrainedby the technology used for its implementation.

• Facts:

• The faster memory is, the greater the cost/bit is.

• (The larger memory is, the slower is it.)

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The Anatomy of a PC – Key Concepts

RAM An acronym for Random Access Memory. It is random because any of the bits or bytes resident in RAM can be accessed nonseqeuntially. RAM is memory that can be both read and written to. The information stored in a semiconductor RAMwill be lost when electrical power is removed.

ROM An acronym for Read-Only Memory. We cannot write new data to those memories. There are several subtypes of ROM: “classical” ROM,

PROM (Programmable ROM),EPROM (Erasable PROM),EEPROM (Electrically EPROM),Flash-EEPROM.

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The Anatomy of a PC – Key Concepts

BIOS An acronym for Basic Input/Output Sytem. A collection of software codes built into a PC. BIOS is stored in ROM (Flash-EEPROM usually) chip on the motherboard.

Boot The process that takes place when a PC is turnedon and it performs the routines necessary to getall the components functioning properly and thenload the operating system.

POST An acronym for Power-On Self-Test, a procedurethe computer goes through when booting toverify that the basic components of a PC arefunctioning.

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The Anatomy of a PC – Key Concepts

CMOS An acronym for Complementary Metal-OxideSemiconductor – a term that describes howa CMOS chip is manufactured. Powered bya small battery, the CMOS memory chip retainscrucial information about what hardware a PC comprises even when the power is turned off.

Clock A microchip that regulates the timing and speedof all the computer’s functions. The chip includesa crystal that vibrates at a certain frequency whenelectricity is applied to it. The speed of clocks –– and therefore computers – is expressed inmegahertz (MHz) or gigahertz (GHz). Thus a PCmay be desribed as having a 1.2 GHz processor,which means that the processor has been designedto work with a clock chip runnig at that speed.

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Types of RAM

• DRAM (Dynamic Random Access Memory)

For years, the most common type of main RAM.

“Dynamic” refers to the memory's method ofstorage – basically storing the charge on a capacitor, which leaks the charge over time and must be refreshed about every thousandthof a second.

• SRAM (Static Random Access Memory)

RAM that, unlike DRAM, doesn't need to have itselectrical charges constantly refreshed. SRAM isusually faster than DRAM but more expensive.

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Memory Modules

Memory module is a small circuit board with the memory chips (RAM). It uses less board space and it is more compact.

• SIMM (Single In-Line Memory Module) 30- or 72-pin

• DIMM (Dual In-Line Memory Module)

• RIMM (Rambus In-Line Memory Module)

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SIMM (72-pin)

DIMM

Memory Modules – cont‘d

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Cache Memory

• The speed of the main memory is relative slow with respect to the today's processors.

• A cache memory is a small, very fast memory that retains copies of recently used information from the main memory.

• Memory caching is effective because the running programs access the same data or instructions over and over.

• Cache capacity is much smaller than main memory (about 1/128 – 1/32 of the main memory capacity).

• Cache memory operates transparently to the programmer, automatically deciding which values to keep and which values to overwrite.

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Cache Memory – cont‘d

• Primary cache (Level 1, L1 cache) is built into the processor chip with a zero wait-state (delay) interface to the processor's execution unit, it is limited in size.

• Secondary cache (Level 2, L2 cache) can be found on the motherboard.

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CPU (processor, microprocessor)

• CPU – Central Processing Unit

• often called the brains of a computer

• CPU is a tight, complex collection of transistors arranged so that they can be used to manipulate data

• most operations of the computer are handled by the processor

• processor manufacturers: Intel, AMD, Cyrix

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CPU – cont'd

According to Moore's Law formulated in 1965 by Gordon Moore (co-founder of Intel), the number of transistors per integrated circuit would double every 18 months. Moore predicted that this trend would hold for the next ten years. In fact, as the graph illustrates, Intel has managed to doggedly follow this law for far longer. In 1978 the 8086 ran at 4.77 MHz and had less than 30,000 transistors. By the end of the millennium the Pentium 4 had a staggering 42 million on-chip transistors and ran at 1.5 GHz.

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CPU – cont'd

Source: www.pctechguide.com

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Processor Registers

• Registers are very fast temporary storage devices typically used to hold intensively used data and intermediate results.

• The set of registers within the CPU represents the top level of the memory hierarchy.

User Visible Registers

• Can be accessed by programmers.

• They are often called general-purpose registers.

Control and Status Registers

• Used by the control unit to control the operation of the CPU; not directly accessible by the programmer.

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Stack

• A list of data elements, with the restriction that elements can be added or removed at one end of the list only. This end is called the top of the stack and the other end is called the bottom.

• Placing a new element on top of the stack is an operation called push; removing the top element is called pop.

• LIFO – Last In First Out

12345 12345

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Data/ L1 Memory InternalType/Generation Year Address Cache Speed Clock

Bus [KB] [MHz] [MHz]8086/First          1978 16/20 bit None 4.77-8 4.77-88088/First 1979 8/20 bit None 4.77-8 4.77-880286/Second 1982 16/24 bit None 6-20 6-2080386DX/Third 1985 32/32 bit None 16-33 16-3380386SX/Third 1988 16/32 bit 8 16-33 16-3380486DX/Fourth 1989 32/32 bit 8 25-50 25-5080486SX/Fourth 1989 32/32 bit 8 25-50 25-5080486DX2/Fourth 1992 32/32 bit 8 25-40 50-8080486DX4/Fourth 1994 32/32 bit 8+8 25-40 75-120Pentium/Fifth 1993 64/32 bit 8+8 60-66 60-200Pentium MMX/Fifth 1997 64/32 bit 16+16 66 166-233Pentium Pro/Sixth 1995 64/36 bit 8+8 66 150-200Pentium II/Sixth 1997 64/36 bit 16+16 66 233-300Pentium II/Sixth 1998 64/36 bit 16+16 66/100 300-450Pentium III/Sixth 1999 64/36 bit 16+16 100 450-600AMD Athlon/Seventh 1999 64/36 bit 64+64 100-200+ 500-600+Pentium 4/Seventh 2000 64/36 bit 12+8 100 1.4 – 2 GHz

„Generations of Processors“

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Block Diagram of the 8086 Processor

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AMD Processors

Athlon

Duron K6-2

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Motherboard (mainboard)

The main circuit board inside the PC which holds• processor,

• main (operational) memory – RAM,

• CMOS memory (it is used to store basic information about the PC's configuration)

• BIOS stored in ROM (usually Flash-EEPROM)

• integrated floppy drive and hard drive controller

• expansion slots (ISA, PCI, AGP, ...)

• I/O ports and other interfaces (parallel and serial port, USB, …)

• connectors to connect other parts of a computer (keyboard, small speaker, reset switch, power LED, CPU fan, …)

...The above-stated information is dependent on the type of motherboard.

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Motherboard (mainboard) – cont'd

Graphics card, soundcard, faxmodem, etc. canbe integrated on the motherboard (“All-In-One” motherboard).

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Expansion (I/O) Buses

• peripherals are connected to the I/O buses in various ways, primarily through connectors directly on the motherboard and through different interfaces such as expansion cards

• I/O bus depends on the type of processor

• slots (connectors of I/O bus) are placed on the motherboard

• different types of I/O buses: ISA, MCA, EISA, VL-Bus, PCI, AGP

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ISA Expansion Bus

ISA – Industry Standard Architecture (also AT-Bus)

• the oldest, slowest and soon to become obsolete I/O bus• designed for 80286 processor

• specifies a 16-bit transfer driven by a 8 MHz clock

• It has a theoretical data transfer rate of up to 16 MBps. Functionally, this rate would reduce by a half to 8 MBps since one bus cycle is required for addressing and a further bus cycle for the 16-bits of data. In the real world it is capable of more like 5 MBps - still sufficient for many peripherals - and the huge number of ISA expansion cards ensured its continued presence into the late 1990s.

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Block Diagram of the ISA Architecture

Processor

L2cache

ISAcontroller

Mainmemory

ISA Bus

Syst

em

bu

s

16-b

itsl

ots

8-b

itsl

ots

(simplified)

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PCI Expansion Bus

PCI – Peripheral Component Interconnect

• designed for 80486 a Pentium processors

• in its original implementation PCI ran at 33 MHz, it was later raised to 66 MHz

• theoretical throughput to 266 MBps (33 times faster then ISA)

• it can be configured both as a 32-bit and a 64-bit bus

• supports the PnP standard (Plug and Play)

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Block Diagram of the PCI Architecture

Processor

L2cache

PCI/ISABridge

Mainmemory

ISA Bus

Syst

em

bus

(simplified)

CPU/PCIBridge

ISA

slo

tsPC

I sl

ots

PCI bus

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PCI Slots

                               

                       

Source: www.howstuffworks.com

ISA Slots

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AGP

AGP – Accelerated Graphics Port

• designed for Pentium II processor

• used for graphics cards only

• significantly speeds the performance in graphics app's (3D graphics, texture mapping and so on)

• operates at the speed of the processor bus

• AGP 1x (264 MBps), AGP 2x (528 MBps), AGP 4x (1056 MBps)

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Block Diagram of the AGP Architecture

Source: www.pctechguide.com

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AGP-based Graphics Card (example)

Source: www.howstuffworks.com

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Parallel Port

• is most often used to connect a printer

• some drives (e.g. ZIP) and other peripherals (e.g. scanner) may piggyback on the parallel port

• Canon connector, 25-pin female, marked LPT or PRN, (interface Centronics)

• standard IEEE 1284 provides bi-directional communication and faster data flow

• Compatible Mode (Centronics), Nibble Mode, Byte Mode, EPP (Enhanced Parallel Port) Mode, ECP (Extended Capabilities Port) Mode

• EPP mode is mostly used

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Serial Port

• is most often used to connect a mouse or a modem

• Canon connector, 9- (or 25-) pin male, marked COM or RS 232

• slower than parallel port

• today's computers usually use a mouse that connects to a PS/2 port (connector)

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USB

• USB – Universal Serial Bus

• up to 127 peripheral devices can be connected

• supports fast data transfer rates

• along with the signal USB carries a 5 V power supply so small devices, such as hand held scanners or speakers, do not have to have their own power cable

• was designed to be user-friendly and it is truly PnP

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Motherboard SL-77KV

Specification www.soltek.com.tw

Processor: AMD Athlon™

Chipset: VIA APOLLO KX133, FSB 200 MHz, AGP 4x

Memory: 3 x 168-pin 3.3V DIMM Sockets, Supports 8MB to 768MB (maximum) DRAM Size, PC 133 compliant

Cache Memory: Built-in to AMD Athlon™ Processor Module

On-Board EIDE: 2 x PCI Bus Master UATA 33/66 IDE ports

(up to 4 ATAPI Devices) Supports for PIO Mode 3, 4,

UATA 33/66 IDE & ATAPI CD-ROM

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On-Board Super I/O: 1 x Floppy Port, 2 x serial ports (high-speed 16550 FIFO UART Ports), 1 x Parallel Port with EEP/ECP/SPP Capabilities, PS/2 Mouse connector, Keyboard connector, 4 x USB Ports

Expansion Slots: 1 x AGP Slot, 1 x AMR Slot, 5 x 32-bit PCI Bus Master Slots, 1 x 16-bit ISA Slots

Form Factor: ATX Form Factor (190mm x 305mm)

BIOS: AWARD Plug-and-Play BIOS Supports Advanced Power Management Function Flash Memory for easy upgrade

Other Features: Supports AGP4x, PC 133 compliant, Ultra ATA/66, AC'97 Audio Function, H/W Monitor

Motherboard SL-77KV – cont'd

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Motherboard SL-77KV – cont'd

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Motherboard SL-77KV – cont'd

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Power Supply

• converts the AC input (230 V) to lower DC voltages (3.3 V, 5 V, 12 V, –5 V, –12 V)

• the 3.3- and 5-volts are typically used by digital circuits, while the 12-volt is used to run motors in disk drives and fans

• the main specification of a power supply is in watts (usually about 250 W or more)

Source: www.howstuffworks.com

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Power Supply – cont'd

According to PC Power & Cooling, Inc., some power consumption values (in watts) for common items ina personal computer are:

AGP card 20 to 30 W PCI card 5 W floppy disk drive 5 W network interface card 4 W 50x CD-ROM drive 10 to 25 W RAM 10 W per 128 MB 5200 RPM IDE hard disk drive 5 to 11W 7200 RPM IDE hard disk drive 5 to 15W Motherboard (without CPU or RAM) 20 to 30W 550 MHz Pentium III 30W 733 MHz Pentium III 23.5W 300 MHz Celeron 18W 600 MHz Athlon 45W

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Input/Output Processing

1. Programmed I/O

• The CPU executes a sequence of instructions, being in direct control of the I/O operations (sensing device status, read/write commands, etc.).

• When the CPU issues a command to the I/O module, it must wait until the I/O operation is complete.

• A lot of waisted time, because the CPU is much faster then devices.

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Input/Output Processing

2. Interrupt-driven I/O

• IRQ – Interrupt Request

• After issuing an I/O command, the CPU has not to wait until the operation has finished; instead of waiting, the CPU continues with other useful work.

• When the I/O operation has been completed, the I/O module issues an interrupt signal on the bus.

• After receiving the interrupt, the CPU moves the data to/from memory, and issues a new command if more data has to be read/written.

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Input/Output Processing

2. Interrupt-driven I/O – cont'd

Advantage over programmed I/O:

• Instead of waiting the operation to be finished, the CPU can do some useful work.

Still a problem:

• If large amounts of data have to be moved, this technique is still not efficient, because the CPU has to take care of each data unit separately, to move it to/from memory.

• Handling the interrupt also takes some time.

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Input/Output Processing

3. Direct Memory Access (DMA)

• An additional module on the system bus, the DMA module (controller), takes care of the I/O transfer for the whole sequence of data.

• The CPU issues a command to the DMA module and transfers to it all the needed information.

• The DMA module performs all the operations – it transfers all the data between I/O module and memory without going through the CPU.

• When the DMA module has finished, it issues an interrupt to the CPU.

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Device Manager – MS Windows 2000

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• http://www.pctechguide.com

• http://www.howstuffworks.com

• http://www.zive.cz

• White, R.: How computers work. Que, Indianapolis 1999.

• Vrátil, Z.: Postavte si PC. BEN, Praha 1999.

• Horák, J.: Učebnice hardware. Computer Press, Praha 1998.

• Precht, M. – Meier, N. – Kleinlein, J.: EDV-Grundwissen: Eine Einführung in Theorie und Praxis der modernen EDV. Addison-Wesley, 1996.

• Колесниченко, О. – Шишигин, И.: Аппаратные средства РС. «БХВ», Санкт-Петербург 1999.

• Вильховченко, С.: Современный компьютер: устройство, выбор, модернизация. «Питер», Санкт-Петербург 2000.

References