Hardware: The CPU & Storage
Microchips, Miniaturization, & Mobility
• Vacuum tubes – used in old radios, light bulb-size electronic tubes with glowing filaments, the
ENIAC (1946) used 18,000 of them, high failure rate, damaged tubes had to be replaced
• Transistor - a tiny electrically operated switch, or gate, that can alternate between “on” and “off”
many millions of times per second, developed by Bell Labs in 1947
• Integrated circuit – an entire electronic circuit formed on a single “chip” usually made of silicon
(semiconductor), solid state device where electrons travel through solid-state material
• Microchips store and process data in all the electronic gadgetry, has millions of micro miniature
electronic circuits, industrial rice, photolithography process
• Processor speed +cache sizes + memory access times affect computer performance.
How the Processor or CPU Works
• A processor, also called the Central Processing Unit (CPU) carries out the basic instructions that
operate a computer.
• The term microprocessor refers to a personal computer processor chip.
• Processors contain the Control Unit (traffic cop) and ALU (performs arithmetic and comparison
• Machine Cycle : Fetch, Decode, Execute, Store
• Word size – The number of bits a processor may process at one time, typical values of 32 and 64 bits,
the larger the word size, the faster the processor (everything else being equal).
• Processor also contains registers (high-speed storage locations)
• Buses – electrical data roadways through which bits are transmitted
• and the system clock. Processors today are generally superscalar.
• Speed measurement units for various computer categories
• Hertz – one clock cycle
• MHz, GHz: millions or billions of clock cycles per sec, for microcomputers
• MIPS: millions of instructions per sec, for workstations, mainframes
• Flops: floating point operations per sec, for supercomputers
• Two principal architectures or designs of microprocessors: (how elementary the instruction sets are)
1. CISC (Complex Instruction Set Computing) - Supports a large number of instructions at relatively
low processing speeds
2. RISC (Reduced Instruction Set Computing) - Used mostly in workstations, a great many seldom-
used instructions are eliminated.
• Two kinds of microprocessors used in most personal computers today:
1. Intel-type chips made by Intel, AMD, and others, used by 90% of computers
• Most high-performance desktop PCs use some type of Pentium processor. Many notebook
computers and Tablet PCs use a Pentium M processor. Less expensive, basic PCs use Celeron.
The Xeon and Itanium are used for workstations and low-end servers.
2. Motorola-type chips are made by Motorola for Apple Macintosh computers. Today’s Apples are
using Intel processors.
• Hyperthreading allows the processor to mimic the power of two processors.
• Dual-core and multi-core processors are now being offered. This is two or more processors on a chip.
• System on a chip integrates the functions of a processor, memory and video card on a chip.
• Parallel processing is a method that uses multiple processors to accomplish a task. (Dual Processors,
• Overclocking refers to the increase of the rate at which a clock ticks to increase computer
• Heat Sinks, heat pipes and liquid cooling
• Chipset – collection of interconnected chips that determine what types of processors, memory, and
video card ports, and other hardware will work on the same motherboard
• Analog vs. Digital.
• Machine language - a binary-type programming language built into the CPU that the computer can
run directly, every higher level language must be translated to machine language before it can be run
by the processor (binary code vs. source code).
• Binary system, bit, byte
• ASCII, EBCDIC, Unicode representations.
• Parity bit – an extra bit attached at the end of a byte to check data accuracy, even and odd, 1-
dimensional vs. 2-dimesional
How Memory Works
• Memory stores: (1) Operating System (2) Application Programs (3) Data
• Types of memory chips:
• RAM (Random Access Memory) – to temporarily store program instructions and data, volatile,
various types: DRAM, SDRAM, DDR-SDRAM, etc.
DRAM – must be constantly re-energized. Other variations are faster than DRAM: Synchronous
DRAM, Double Data Rate SDRAM.
SRAM – static RAM chips are faster and more reliable than DRAM chips. SRAM do not have to
be energized as often as DRAM.
RDRAM (Rambus DRAM)– faster yet because it uses pipelining.
MRAM – a newer type of RAM (magnetoresistive RAM) stores data using magnetic charges
rather than electrical charges. As the cost of MRAM goes down one can expect MRAM to
replace DRAM and SRAM chips.
Memory modules – small circuit boards that can be plugged into the motherboard to provide
SIMM (Single inline memory module), DIMM (Dual inline memory module), RIMM (Rambus
inline memory module)
RAM Configurations – 512 MB (generally, range today is between 256 MB and 16 GB)
How Cache Works: Level 1 (Internal) & Level 2 (External or Internal)
• Cache - temporary storage for instructions and data that the processor is likely to use frequently, thus
speeding up processing
1. Level 1 (L1) cache – part of the processor chip, 32KB, 64KB
2. Level 2 (L2) cache – can be a part of the microprocessor chip (ATC- Advanced Transfer Cache),
64KB to 16MB
3. PC can have Level 3
• ROM (Read Only Memory) – to store fixed start-up instructions such as the BIOS, non-volatile
Many devices also contain ROM chips: printers (containing data for fonts)
• ROM chips are also called firmware.
• PROM – programmable by user. EEPROM
• Flash – to store flexible programs, non-volatile, similar to EEPROM
• CMOS – to store flexible start-up instructions such as time, date, and calendar, powered by a
• Virtual memory - free hard-disk space used to extend the capacity of RAM
• Memory hierarchy
• Memory Access – measured in both nanoseconds or Hz (533 MHz DDR SDRAM)
• Converting from MHz to nanoseconds 1,000,000,000 ns / 533,000,000
• SDRAM – ceiling of 133 MHz (7.5 ns)
• DDR-SDRAM – ceiling of 677 MHz (1.5 ns)
• RDRAM – ceiling of 1600 MHz (.625 ns)
• ROM access time range is 25-250 ns.
Expandability: Buses, Cards, and Ports
• Expansion slots (adapter slots) - sockets on the motherboard into which you can plug expansion
• Expansion cards (adapter cards)- circuit boards that provide more memory or that control peripheral
devices. Some motherboards include all necessary capabilities and do not require any adapter cards.
• Graphics (Video) card - for monitors
• Graphics accelerator card – increases the speed at which graphics are displayed
• Video capture card – connects a camcorder
• Sound card - for speakers and audio output, audio input
• MIDI card – connects musical instruments
• Modem card - for remote communication via phone lines
• Network interface card - for remote communication via cable, connects to other computers
• PC to TV converter card – connects a television
• TV tuner card – allows viewing of television channels on the monitor
• Disk controller – connects disk drives
• Plug and play
• Hot plugging – do not have to open the system unit or restart the computer to use a new device.
• Special kind of card: PC card - for mobile computing devices, used to expand capabilities three
types (I – flash memory card 64MB-5GB , II – modems and NICs, III – hard disk drives and
wireless communications) differing in thickness and usage – available in a variety of shapes and
sizes. Another type of flash memory is a USB flash drive also 64MB-5GB
• Port – connecting socket or jack on the outside of the system unit into which different kinds of cables/
peripherals can plug. Newer PCs have ports in both the front and back of the computer.
• Serial ports – sends one bit at a time, used with keyboards, modems, and mice (do not req2uire
fast transmission rates)
• Parallel ports – transmits 8 bits at a time, used with printers and external disks
• USB ports (Universal Serial Bus) – allows automatic configuration while peripheral devices or
cards are being installed, allow daisy chains of up to 127 devices. Typically 6 to 8 on a computer.
USB 2.0 (40 times faster). USB Hub (daisy-chaining, tree structure)
• Firewire ports – designed to compete with USB, used with camcorders, DVD players, and TVs,
hot pluggable, requires special card. One may attach devices requiring faster transmission speeds.
Firewire Hub. Some newer peripherals only attach to a Firewire port.
• Traditional port to Firewire and USB (which can be replaced by which)
• SCSI (Small Computer System Interface) ports – up to 32 bits at a time, daisy chain of devices
Traditional Ports are serviced by:
SCSI, Parallel, Audio -> Firewire
SCSI, Parallel, Audio, Serial, Mouse - > USB.
• Dedicated ports – ports for special purposes: keyboard, mouse,
• Infrared ports (IrDA) – infrared, make wireless connections, line of sight, short distance
• Bluetooth port - radio waves, alternative to IrDA. Bluetooth-enabled (does not require LOS).
Bluetooth wireless port adapter can be purchased and attached to a USB port, Bluetooth cards for
• Common buses: input devices to motherboard, connect memory to processor, processor to memory,
and connect memory to output or storage. Size of bus is width, the number of bits that can be
transferred at the same time. If a number in memory is stored in 8 bytes…32 vs. 64 bit bus. 64bit
processor means that data can be transferred in the processor in 64 bit chunks (word size of the
processor). The second measure is bus clock speed. Most of today’s processors have a bus clock speed
of 400, 533 or 800 MHz. Two basic types of buses: system bus and expansion bus
• Expansion buses – the types of expansion buses on a computer determine the types of cards you can
attach to your computer. PCI, AGP, USB Firewire, PC Card
• ISA bus – 8 or16 bits wide, slowest at transmitting data, used for mice, modems, low-speed
• PCI (Peripheral Component Interconnect) bus – 32 or 64 bits wide, used with graphic cards,
sound cards, modems (Network cards), SCSI cards
• AGP (Accelerated Graphics Port) bus – designed to support video transmission and 3D
graphics, 2x speed of PCI.
• USB bus and Firewire bus eliminate the need to install cards in expansion slots. USB port
attaches to USB, bus which connect to PCI bus on the motherboard.
• PC Card Bus – also connects to PCI bus
• PCI Express is a bus with a faster transfer rate and is meant to replace PCI and AGP expansion
• Drive Bays – for additional storage drives
• Power Supply – Alternating Current (AC) needs to be converted to Direct Current (DC). If the power
supply does not provide consistent power, the computer will not function properly. Fan is also built-in.
Additional fans may be in system unit. Most system units have at least three fans: power supply, case,
processor (heat sink)
• Measurements: capacity, access time (milliseconds), transfer rate (KBps, MBps), rpm (5400-15000)
• Floppy disks – disks made of mylar plastic, low storage capacity (1.44 MB)
• Zip disk – can plug into USB or Firewire port
• Hard disk - thin but rigid metal, glass, or ceramic platters covered with a substance that allows data
(bits) to be held in the form of magnetized spots. Read/Write head, write-protection
• Longitudinal recording,
• Perpendicular recording. (80-500 GB, up to 10 times the storage capacity of drives using
longitudinal recording techniques). Thermal energy can reverse magnetization.
• Thermo-mechanical storage technique – tiny depressions can be created, read and erased with a
micromechanical tip. Requires higher heat (25 terabits on a postage stamp sized area, 25 DVDs, IBM’s
• Disk caching (disk buffer)
• Head crash – Spinning creates space between Read/Write head and platter. A head crash happens
when the surface of the read/write head comes into contact with the surface of the hard-disk platter,
causing the loss of some or all of the data on the disk. When platters are not in motion the read/write
head rest on the platter in an area called the “landing zone” where no data is ever stored.
• Fixed hard disks - housed in a microcomputer system unit and used to store nearly all programs and
most data files, can be external connecting through the USB port. Rotational inertia is used to safely
park the read/write heads.
• External, Removable hard disks (>500 GB) – plugs into a USB or Firewire port, one or two platters
enclosed along with read/write heads in a hard plastic case, which is inserted into a microcomputer’s
cartridge drive, used typically for backup
• Removable packs, fixed disk drives, and RAID (Redundant Array of Inexpensive Disks) for large
computer systems. Data is sent along several parallel paths simultaneously.
Optical Disks: CDs & DVDs
• Optical disk – It is a removable disk on which data is written and read through the use of laser beams
(note uses different technology than hard disks). Three generations of optical disk, Pits and lands, uses
a spiral track.
• Unit of Measure: X represents 150KBps which was the speed of the data transfer rate of the original
CD-ROM. Measurements are now written as 56X Max, for example.
• Writing Data to an optical disk:
• A higher-powered laser light creates pits.
• Reading Data from an optical disk:
• A lower-powered laser shines a light beam toward the disk.
• If light strikes a pit it scatters. If light strikes a land it is reflected back to the laser.
• Reflected light is translated into a digital signal of 1 and sent to the computer. Absence of
reflected light is read as a 0.
• First Generation
• CD-ROM - read only. For pre-recorded text, graphics, and sound
• CD-R - for recording on once
• CD-RW - for rewriting many times
• Second Generation
• DVD-ROM - for reading only
• DVD-R - for recording on once
• For rewriting many times: DVD-RW, DVD-RAM, DVD+RW
• Historically the world was split into 6 DVD zones. Newer DVD players are no longer region-
• Third Generation
• Blu-ray and HD-DVD (two incompatible recording formats)
• Holographic Versatile still in research and would greatly increase storage over Blu-ray and HD-
Other Types of Storage
• Smart card - looks like a credit card but contains a microprocessor embedded in the card memory
with a microprocessor. Storage capacity is, on average, 250 pages of data.
• Optical cards (CD technology) - plastic, laser-recordable, wallet-type card used with an optical-card
reader. Storage capacity is about 2000 pages.
• Flash memory card, flash drives - solid state medium, no moving parts, circuitry on credit-card-
size PC card that can be inserted into slots connecting to the motherboard on notebook computers