U1 - CPU Flashcards
WHAT ARE TRANSISTORS ?
Tiny switches that control the flow or current. Current represent 1 and no current 0
WHAT ARE TRANSISTORS STORED ON ?
Slices of silicon
A single chip can contain thousands of transistors
DESCRIBE F-D-E USING VON NEUMANN ARCHITECTURE
Data from currently running instructions are stored in binary in the main memory
Instructions are fetched from the memory into the CPU one at a time
The instruction is decoded and run
The next instruction is fetched from memory
Data is fetched as and when needed
WHAT IS VON NEUMANN ARCHITECTURE ?
The design on which general purpose computers are based
NAME 5 REGISTERS
Program Counter
Memory Address Register
Memory Data Register
Current Instruction Register
Accumulator
WHAT IS A REGISTER ?
A fast access temporary storage location in the CPU
WHAT DOES A PC DO ?
Program Counter
Keeps track of the memory ADDRESS of the NEXT instruction
WHAT DOES THE MAR DO ?
Memory Address Register
Holds the ADDRESS of the instruction CURRENT instruction
WHAT DOES THE CIR DO ?
Current Instruction Register
TEMPORARY holding area for the INSTRUCTION that is being decoded
WHAT DOES THE MDR DO ?
Memory Data Register
TEMPORARILY stores data that has been fetched from memory
WHAT DOES THE ACCUMULATOR DO ?
Register in ALU that holds the RESULTS of currently running instructions
NAME THE 4 CPU COMPONENTS
Registers
Control Unit
ALU
Memory
CONTROL UNIT
Directs the flow of data
Coordinates all parts of the CPU
Controls clock
ALU
Arithmetic Logic Unit
Performs all calculations and logical operations within the CPU
NAME 3 BUSES
Address Bus
Data Bus
Control Bus
WHAT DOES THE ADDRESS BUS DO ?
When data is saved or loaded from memory, the address it is stored at must be sent
Memory address travel on the address bus
GOES BETWEEN INTERNAL MEMORY AND RAM
WHAT DOES THE DATA BUS DO ?
When data is sent between different parts of the computer it is sent on the data bus
WHAT DOES THE CONTROL BUS ?
The CU uses this bus to send control signals to different parts of the computer
FETCH
The CPU reads the PC to locate the address of the instruction. The PC value is COPIED TO THE MAR and sent on the address bus. The CU tells the RAM to check the A-Bus and send the INSTRUCTION at that location on the DATA BUS to the MDR
DECODE
The CU AUTHENTICATES THE INSTRUCTION in the CIR.
The instruction is decoded to determine the ACTION THAT NEEDS TO BE CARRIED OUT
EXECUTE
SIGNALS ARE sent to different parts of the CPU to execute the instruction.
Sent via the CONTROL BUS.
Any arithmetic or logic functions are performed in the ALU
WHAT 3 FACTORS AFFECT PERFORMANCE ?
CACHE
CLOCK SPEED
CORES
WHAT DOES CACHE DO ?
Holds frequently used instructions
Improves performance as more cache means more frequently used instructions available quicker
Increase hit rate
INCREDIBLY FAST BUT VOLATILE AND EXPENSIVE MEMORY used in the CPU
CLOCK SPEED
Number of F-D-E cycles a CPU can run per second
FASTER CLOCK SPEED = MORE INSTRUCTIONS EXECUTED
Measured in Hertz
OVERCLOCKING can strain battery and requires a cooling system
CORES
Multiple processors can run parallel, sequentially or can multitask
Double cores should mean double the processing power
However sometimes slowed by having to wait on other cores.
No better than one core
WHAT IS RISC ?
ADV/DIS
RISC = Reduced Instruction Set Computer
Processes a limited number of simple instructions
Complex instructions must be broken
ADV - Less circuitry, uses less power
Physically smaller and doesn’t require a dedicated cooling system
Cheaper and less complex to make
Ideal for phones and embedded systems
WHAT IS CISC ?
ADV/DIS
CISC = Complex Instruction Set Computer
Can process complex instructions quickly
Used in computers
DISADVANTAGES - More expensive
Requires more complex circuitry
Physically larger
Use more power and requires a dedicated cooling system
DEFINE AN INPUT DEVICE ?
Allow the user to interact with computer by entering text or sound (data)
DEFINE AN OUTPUT DEVICE ?
Provides the results of the computer’s processing to the user. DISPLAYS THEM
NAME SOME SPECIALIST I/O DEVICES
Braille Printer
Barcode Scanner
WHAT ARE THE 4 KINDS OF PRIMARY STORAGE ?
RAM
ROM
FLASH
CACHE
What is RAM ?
Random Access Memory
A TEMPORARY storage for currently running programs and data e.g. the OS
RAM consists of many store locations each of which has unique address
IS RAM VOLATILE ?
RAM IS VOLATILE
What is ROM ?
Read Only Memory
Used for the PERMANENT storage of data
The data cannot be changed ‘READ ONLY’
ROM stores the BIOS, disadvantage is that BIOS can’t be updated
IS ROM VOLATILE ?
ROM IS NON-VOLATILE
WHAT IS FLASH ? (PRIMARY)
Used for the PERMANENT storage of data and INSTRUCTIONS
It is NON-VOLATILE
Data can be edited in flash memory
The BIOS can be stored and UPGRADED there
WHAT IS CACHE ?
Used for the TEMPORARY storage of frequently accessed data and instructions
Small number of store locations
Can be accessed quickly by the CPU
VOLATILE
FASTEST STORAGE TYPE
WHAT IS SECONDARY STORAGE ?
A non-volatile, LONG-TERM storage that is not accessed directly by the CPU
When DATA is needed it is transferred into PRIMARY STORAGE
Data is put into secondary memory when it is not being actively used
It takes longer to access secondary memory stores than primary
WHAT ARE THE 3 KINDS OF SECONDARY STORAGE TYPES ?
OPTICAL
MAGNETIC
FLASH
HOW DOES OPTICAL STORAGE WORK ?
EXAMPLES ?
CD, BLU-RAY, DVD
Laser beams are projected onto the disc, if light is reflected it is one, if light is not reflected it is zero
HOW DOES MAGNETIC STORAGE WORK ?
EXAMPLES ?
Discs are magnetised + or -, equating to 0 or 1
Data is stored and read using a READ/WRITE HEAD and a magnetic platter
CASSETTE TAPES, VHS, HDDs
HOW DOES FLASH STORAGE WORK ?
EXAMPLES ? (SECONDARY)
Also called SOLID STATE DRIVES because there are no moving parts
Flash works by sending a large current to force electrons through a barrier the electron arrangement gives the data
SD cards, USBS, SSDs
HDD - PROS/CONS
PRO - Good compromise between storage capacity and cost
CON - Speed does not come close to RAM/ SSDs
SSDs - PROS/CONS
PRO - Quicker start up than HDD
Consume less power and are lighter are smaller than HDD
CON - SSDs are more expensive
CD / DVD
PRO - Two-layered storage
CONS - Easily scratched going out of fashion
NAME THE DATA TYPES IN ORDER
Byte = 8 bits / 4 nibbles
Kilobyte - 1024 bytes
Megabyte - 1024 Kb
Gigabyte - 1024 MB
Terabyte - 1024 KB
Petabyte - 1024 TB
Exabyte - 1024 PB
Zetabyte - 1024 EB
Yottabye - 1024 ZB
WHAT DOES GPU STAND FOR ?
GRAPHICS PROCESSING UNIT
WHAT DOES A GPU DO ?
Generates and controls the output to the screen
INTEGRATED GPU
An integrated GPU is placed on the same chip as the CPU.
It relies on the system’s memory for graphics processing
ADV / DISADV OF A DEDICATED GPU
A discrete graphics card is separate form the CPU and has its own video memory to provide HIGH GRAPHICS PROCESSING POWER
Uses more power and generates more heat
Used by professional graphic designers and gamers
WHAT IS A SOUNDCARD ?
Canbe fitted onto the motherboard or PCI slot
They enable the computer to output sound
Sound cards converts analogue inputs into digital sound and reverse this process fro sound output
WHAT IS THE MOTHERBOARD ?
The main circuit board of the computer.
CPU & ROM will be mounted onto the motherboard
It provides space for RAM expansion slots, USB ports and PCI slots for extension cards, and controllers for devices
WHAT IS AN EMBEDDED SYSTEM ?
EXAMPLES ?
A combination of hardware and software that performs a specific task
Fitbits / Washing Machines
An embedded system are reactive, they respond to conditions in their environment, i.e. temperature & weight
WHAT IS SOFTWARE WRITTEN FOR AN EMBEDDED SYSTEM CALLED ?
FIRMWARE
WHERE IS DATA STORED IN EMBEDDED SYSTEMS ?
ROM or FLASH
