Architecture of a CPU
What actions occur at each stage of the fetch-execute cycle
- The role/purpose of each component and what it manages,
stores, or controls during the fetch-execute cycle
- The purpose of each register, what it stores (data or address)
- The difference between storing data and an address
Not required
- Knowledge of passing of data between registers in each stage
Computer System-overall computer including the mouse and keyboard
Input-used to control the main device
Output-for the user.Is feedback from a device.
CPU-controls and contains the whole computer system (central processing
unit). It processes instructions and runs programmes. The CPU is
connected to: ⤵
● Main Memory- a temporary space to open files and applications.
● Secondary Storage- saves information for the long term.
● Input Devices- used to control
● Output devices- gives feedback
Von Neumann architecture
This is the way in which computers store data
and instructions in the same place making them
indistinguishable from one another. The CPU
must decide what an instruction is and what is
data. (How it works) ➡
The CPU is made up of: ⤵
,● Registers- They carry out operations from the control unit and the
ALU. It's a fast and temporary memory location in the CPU. There are
four main types of registers: ⤵
○ PC- Holds the address (label) of the next instruction to be
executed.
○ ACC- Stores the results of calculations from the ALU and the
values of inputs and outputs from the CPU.
○ MAR- stores the address (location) of data currently being
used or an instruction to be decoded and executed in memory
or where the MDR needs to fetch data from.
○ MDR- stores data that needs to be transferred and stored in
memory. Also stores data fetched from memory.
● The Control unit- controls and processes logical information.
● The Arithmetic Logic unit (ALU)- processes the arithmetic and logical
things. Helps the control unit to speed up the computer.
● Cache- stores the more frequent information. Makes it more quicker
to access than RAM but slower than registers. Only temporary
storage.
1. The address of an instruction is copied from the PC to the MAR.
2. The control Unit fetches the data of the address and copies it to the
MDR,
3. The PC is ready to point to the next instruction for the Fetch-Execute
Cycle. (incremented)
, 4. The MDR contains data from memory or an instruction. The control
unit decodes the instruction to see what to do.
5. The instruction is executed. This could mean a calculation using the
ALU, locating data in memory, changing the program counter value
etc.
CPU Performance
- Understanding of each characteristic as listed
- The effects of changing any of the common characteristics on system
performance, either individually or in combination.
- What embedded systems are
- Typical characteristics of embedded systems
- Familiarity with a range of different embedded systems
Factors affecting the CPU performance are:⤵
● Clock speed- everything in a computer happens on the pulse of the
internal clock. (The higher the clock speed the faster the instructions
are carried out processed and executed per second improving the
performance of the CPU) This is measured in Hz (an instruction per
second)
● Number of cores- a dual core processor has 2 processors in the
same integrated circuit, linked together. This allows twice as many
instructions to be executed.
● Cache memory- this can be accessed faster than ram. More cache
means faster computer performance.
Increased number of RAM an SSD and HDD also improve the performance
of a computer
Embedded Systems
An embedded computer is a single microprocessor that includes RAM,
ROM and a CPU. e.g. cruise control and engine cooling fans in cars. Or a
computer inside a device.
, Characteristic Embedded systems General purpose
machine
CPU speed Typically slow Very fast
Software Has one purpose and New software can be
can’t install new installed
software
Reliability Very reliable Less reliable- runs
many software
problems.
Embedded systems are built into larger machines
RAM and ROM
- Why computers have primary storage
-- How this usually consists of ROM and RAM
- Key characteristics of RAM and ROM
- Why virtual memory may be needed in a system
- How virtual memory works
-- Transfer of data between RAM and HDD when RAM is filled
RAM and ROM are examples of primary storage- storing data currently.
RAM is read and write data but ROM is read only.
The computer stores running programmes and data in RAM when a
computer is turned on. When turned off, the data stored in RAM is lost
(RAM is volatile as it loses data if power is lost)
All programmes and data are stored permanently on the hard drive. (the
hard drive is non volatile as it doesn’t lose data when power is turned off)
RAM is used in modern computers to store:
● The data/file currently being used (Data and file are the same)
● The programme currently running
● The operating system
What actions occur at each stage of the fetch-execute cycle
- The role/purpose of each component and what it manages,
stores, or controls during the fetch-execute cycle
- The purpose of each register, what it stores (data or address)
- The difference between storing data and an address
Not required
- Knowledge of passing of data between registers in each stage
Computer System-overall computer including the mouse and keyboard
Input-used to control the main device
Output-for the user.Is feedback from a device.
CPU-controls and contains the whole computer system (central processing
unit). It processes instructions and runs programmes. The CPU is
connected to: ⤵
● Main Memory- a temporary space to open files and applications.
● Secondary Storage- saves information for the long term.
● Input Devices- used to control
● Output devices- gives feedback
Von Neumann architecture
This is the way in which computers store data
and instructions in the same place making them
indistinguishable from one another. The CPU
must decide what an instruction is and what is
data. (How it works) ➡
The CPU is made up of: ⤵
,● Registers- They carry out operations from the control unit and the
ALU. It's a fast and temporary memory location in the CPU. There are
four main types of registers: ⤵
○ PC- Holds the address (label) of the next instruction to be
executed.
○ ACC- Stores the results of calculations from the ALU and the
values of inputs and outputs from the CPU.
○ MAR- stores the address (location) of data currently being
used or an instruction to be decoded and executed in memory
or where the MDR needs to fetch data from.
○ MDR- stores data that needs to be transferred and stored in
memory. Also stores data fetched from memory.
● The Control unit- controls and processes logical information.
● The Arithmetic Logic unit (ALU)- processes the arithmetic and logical
things. Helps the control unit to speed up the computer.
● Cache- stores the more frequent information. Makes it more quicker
to access than RAM but slower than registers. Only temporary
storage.
1. The address of an instruction is copied from the PC to the MAR.
2. The control Unit fetches the data of the address and copies it to the
MDR,
3. The PC is ready to point to the next instruction for the Fetch-Execute
Cycle. (incremented)
, 4. The MDR contains data from memory or an instruction. The control
unit decodes the instruction to see what to do.
5. The instruction is executed. This could mean a calculation using the
ALU, locating data in memory, changing the program counter value
etc.
CPU Performance
- Understanding of each characteristic as listed
- The effects of changing any of the common characteristics on system
performance, either individually or in combination.
- What embedded systems are
- Typical characteristics of embedded systems
- Familiarity with a range of different embedded systems
Factors affecting the CPU performance are:⤵
● Clock speed- everything in a computer happens on the pulse of the
internal clock. (The higher the clock speed the faster the instructions
are carried out processed and executed per second improving the
performance of the CPU) This is measured in Hz (an instruction per
second)
● Number of cores- a dual core processor has 2 processors in the
same integrated circuit, linked together. This allows twice as many
instructions to be executed.
● Cache memory- this can be accessed faster than ram. More cache
means faster computer performance.
Increased number of RAM an SSD and HDD also improve the performance
of a computer
Embedded Systems
An embedded computer is a single microprocessor that includes RAM,
ROM and a CPU. e.g. cruise control and engine cooling fans in cars. Or a
computer inside a device.
, Characteristic Embedded systems General purpose
machine
CPU speed Typically slow Very fast
Software Has one purpose and New software can be
can’t install new installed
software
Reliability Very reliable Less reliable- runs
many software
problems.
Embedded systems are built into larger machines
RAM and ROM
- Why computers have primary storage
-- How this usually consists of ROM and RAM
- Key characteristics of RAM and ROM
- Why virtual memory may be needed in a system
- How virtual memory works
-- Transfer of data between RAM and HDD when RAM is filled
RAM and ROM are examples of primary storage- storing data currently.
RAM is read and write data but ROM is read only.
The computer stores running programmes and data in RAM when a
computer is turned on. When turned off, the data stored in RAM is lost
(RAM is volatile as it loses data if power is lost)
All programmes and data are stored permanently on the hard drive. (the
hard drive is non volatile as it doesn’t lose data when power is turned off)
RAM is used in modern computers to store:
● The data/file currently being used (Data and file are the same)
● The programme currently running
● The operating system
