Systems Architecture Flashcards
1
Q
What is a computer system?
A
- A computer system takes a set of digital inputs, processes them and creates a set of outputs
- This is done by using a combination of hardware and software
2
Q
What is a General Purpose System?
A
General Purpose Systems:
- Performs many varied tasks by making use of software applications
e. g. a tablet can be used to listen to music, view web pages, use camera software and create documents
3
Q
What is an Embedded System?
A
Embedded System:
- Performs one specific task within a larger system
- Don’t have a monitor, keyboard or touch screen. They are built on a single printed circuit board
- They are made up of both hardware and the software that they need to do their task. This is called ‘Firmware’.
4
Q
Why Von Neumann Architecture?
A
- Before the VN Architecture, computers were designed to do 1 specific task (‘fixed program’ machines). The program was part of the machine.
- If you wanted the computer to do a different task it literally had to be rewired. This was long and difficult.
5
Q
What is Von Neumann Architecture?
A
- The Von Neumann architecture means that program instructions & data are both stored in computer memory (RAM).
- The CPU can now change tasks simply by loading a different program into memory - no rewiring needed.
6
Q
What are some features of the Von Neumann Architecture?
A
- RAM: There needs to be enough memory for both programs and data
- Buses: Data and instructions are carried on buses
- ALU: responsible for carrying out calculations and logic comparisons
- Registers: small, very fast type of memory, inside the CPU.
- Input & Output: There is a way to input data into the computer and to output info
7
Q
What is the Harvard Architecture?
A
- Harvard Architecture has the idea of keeping data and instructions in separate memory
- Disadvantages: Costly & Complex
8
Q
What is the Memory Data Register?
A
- When the CPU needs to fetch an instruction/data from RAM, it’s initially stored in the MDR
- It is then moved from the MDR to the relevant register in order to be processed
9
Q
What is the Instruction Register?
A
- Having fetched an instruction from RAM (which is stored in the MDR), it is then transferred to the Instruction Register to be decoded and executed.
10
Q
What is the Program Counter?
A
- The PC is used to identify the location of the next instruction/data to be executed by the CPU.
11
Q
What is the Memory Address Register?
A
- The MAR is updated by the PC to contain the location of the next instruction/data to be fetched from RAM
- This address is passed to RAM via the address bus
12
Q
What is the Accumulator?
A
- A register used to temporarily store data whilst calculations are being performed within the ALU.
13
Q
What is the Fetch-Decode-Execute Cycle?
A
The FDE cycle is the process that a CPU follows to execute instructions.
14
Q
What is the Fetch step of the FDE cycle?
A
- The program is loaded into RAM by the operating system. The operating system notifies the CPU where it can find the first instruction in RAM.
- The location is loaded into the Program Counter and the fetch cycle begins.
- The address location in the PC is copied into the MAR. The CU then loads the address from the MAR to the address bus.
- RAM reads the contents on the bus and looks up the contents stored at the location which is then loaded into the data bus.
- The MDR receives the data, the instruction is then copied into the instruction register.
- The PC is now incremented by 1 location.
15
Q
What is the Decode step of the FDE cycle?
A
- While the next fetch cycle begins, the CPU simultaneously is decoding the first instruction. The Control Unit reads the contents of the instruction register.
- It checks if the instruction is valid or not
- If for some reason the instruction was not valid then it would not recognize it and if this were to happen the program will probably turn off and crash
