What is Inside and Outside a System Unit?
- motherboard
- CPU
- memory
- storage
- communications & input / output (I/O)
- slots / cables
The System Unit
The Processor
- The control unit directs & coordinates most operations in the computer. It deciphers instructions and carries them out
- The arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations
The Processor
- The processor contains registers, that temporarily hold data and instructions
- The system clock controls the timing of all computer operations
- The pace of the system clock is called the clock speed, and is measured in gigahertz (GHz)
The Machine Cycle
For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle
Chips
Microprocessor
- Motherboard controls what the computer does
- The brain is the microprocessor chip
- The transistors are the key part of the microprocessor chip
- Intel Pentium / Celeron , AMD Athlon
Chipset
- Motherboard chips that control the information flow from the processor & the other system components
- a computer chip is a small piece of semi-conducting material normally silicon
- integrated circuits are etched onto the chip
- these circuits contain pathways for carrying an electronic current
- they contain resisters, capacitors and transistors.
Moore’s Law – Gordon Moore predicted the number of transistors on a silicon chip will double every 18 months. Transistors on a chip
- 1961 4
- 1971 2,300
- 1979 30,000
- 1997 7.5 million
- 2008 2 billion
- now?
Processor speed
- GHz gigahertz a billion cycles per second
- Other measurements for speed include:
- MIPS (million instructions per second)
- FLOPS (floating point operations per second)
Example:
- 280 teraflops = 280 trillion ops. per sec.
- 1 petaflop = 1,000 trillion ops. per sec.
- Millisecond = 1/1000 second (thousand)
- Microsecond = 1/1,000,000 second (million)
- Nanosecond = 1/1,000,000,000 second (billion)
- Picosecond = 1/1,000,000,000,000 second (trillion)
- Dual-core processors
- Quad-core processors
- Multi-core processors
- faster processors require
- more power and
- produce more heat
- each core is treated by the operating system as a processor
- e.g. dual-core 2 cores on one chip
- dual-core not as fast as two single-core processors but not too far away
- good for running several programs at the same time
Processing
- Word Size – The number of bits the processor can process at any one time
- Registers – High-speed storage areas that temporarily store data during processing
- Buses – transmit bits within the CPU and between CPU and other motherboard components
Memory
- consists of electronic components
- that store instructions
- waiting to be executed by the processor,
- data needed by those instructions, and
- the results of processing the data
RAM chips
- reside on a memory module
- inserted into memory slots
Memory consists of electronic components that store
- instructions waiting to be executed by the processor,
- data needed by those instructions, and
- the results of processing the data
Stores three basic categories of items:
- The operating system and other system software
- Application programs
- Data being processed and the resulting information
- Each location in memory has an address
- Memory size is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB)
- petabyte: 1 quadrillion bytes
- exabyte: 1 quintillion bytes
How does memory work?
- Primary storage = “memory,” “main memory,” “RAM”; this type of memory is temporary and volatile
- Secondary storage = “storage” disks and tape; this type of memory is relatively permanent and nonvolatile
- Volatile memory
- Loses its contents when power is turned off
- Example includes RAM
- Nonvolatile memory
- Does not lose contents when power is removed
- Examples include ROM, flash memory, and CMOS
Types of memory
1.Random Access Memory chips are volatile and hold:
- a.Software instructions
- b.Data before & after the CPU processes it
2.Read only memory
- a.Cannot be written on or erased without special equipment
- b.Are loaded at factory with fixed start-up instructions
3.Complementary Metal Oxide Semiconductor (CMOS)
- a.Powered by a battery
- b.Contains time, date, calendar, boot password
4.Flash memory – Nonvolatile memory that can be erased and reprogrammed more than once
- a.Doesn’t require a battery
- b.Used in newer PCs for BIOS instructions
- Flash memory can be erased electronically and rewritten
- CMOS technology provides high speeds and consumes little power
Cache memory speeds the processes of the computer because it stores frequently used instructions and data
Access time is the amount of time it takes the processor to read from memory
- Measured in nanoseconds
Processing
The CPU works much faster than RAM
Cache temporarily stores instructions and data that the processor uses frequently to speed up processing
- Level 1 cache is part of the microprocessor
- Level 2 cache is SRAM external cache
- Level 3 cache is on the motherboard
- Virtual Memory—also used to speed up processing
- This type of memory is unused hard disk or optical (CD) space that the processor uses to extend the capacity of RAM
- The processor goes first to L1 cache, then L2 cache, then RAM, then virtual memory
- Each type of memory is slower than its predecessor
- 1.Interleaving
- 2.Bursting
- 3.Pipelining
- 4.Superscalar Architecture
- 5.Hyper-threading
- 1.CPU alternates communications between two or more memory banks
- 2.CPU grabs a block of data from memory instead of retrieving one piece at a time
- 3.CPU doesn’t wait for one instruction to complete before fetching its next instruction
- 4.The computer can execute more than one instruction per clock cycle
- 5.A technique used in superscalar architecture in which the OS treats the microprocessor as though it is two microprocessors
Most current personal computers support pipelining
- Processor begins fetching a second instruction before it completes the machine cycle for the first instruction
Parallel processing uses multiple processors simultaneously to execute a single program or task
- Massively parallel processing involves hundreds or thousands of processors
Storage
- Hard Drives (SATA)
- solid State Drives (SSD)
- USB sticks
- External Hard Drives
- Flash memory
- Magnetic tape
- Optical disks (CD/DVDs)
- Online secondary storage
- Speed – large quantities processed quickly & accurately
- Capacity
- Cost of storage – cost per megabytes
- Other factors – reliability, permanence
- 1.M-RAM
- 2.OUM
- 3.Nano-technology
- 4.Optical Computing
- 5.DNA Computing
- 6.Quantum Computing
Description of Processing Technology
- 1.Magnetic RAM uses miniscule magnets rather than electrical charges
- 2.Ovonic Multiplied Memory stores bits by generating different levels of low and high resistance on a glossy material
- 3.Tiny machines work at a molecular level to make nano-circuits
- 4.Uses lasers and light, not electricity. Uses strands of synthetic DNA to store data
- 5.Based on quantum mechanics and stores information using particle states