Section One: Components of a Computer System Flashcards
Register
A very small piece of memory that holds tiny bits of data needed by the CPU. It has very fast read/write speeds.
Fetch
- Copy memory address from the program counter to the MAR.
- Copy the instruction stored in the MAR address to the MDR address
- Increment the program counter to point to the address of the next instruction, ready for the next cycle.
PC
Program Counter
-Holds the memory address of the instruction for each cycle.
Decode
The instruction in the MDR is decoded by the CU.
The CU may then prepare for the next step - eg by loading values into the MAR or MDR
Execute
The instruction is performed.
This could be: load data from memory, write data to memory, do a calculation or logic operation, change the address in the PC, or halt the program.
CU
Control Unit
- In overall control of the CPU
- Executes program instructions by following the FDE cycle.
- Controls the flow of data inside and outside the CPU
Cache
- Very fast memory in the CPU.
- Slower than the registers but faster than RAM.
- Stores regularly used data so that the CPU can access it quickly.
- They have a very low capacity and are expensive.
- Larger cache gives the CPU faster access to more data.
ACC
Accumulator
-Stores intermediate results of calculations in the ALU
Number of Cores
Each core in a CPU can process data independently of the rest.
The more cores in a CPU has, the more instructions it can carry out at once, so the faster it can process a batch of data.
The CPU…
… depends on…
Processes all of the data and instructions that make the systems work.
The processing power of a CPU DEPENDS ON its clock speed, cache size and number of cores.
MAR
Memory Address Register
-Holds any memory address about to be used by the CPU. The address might point to data or a CPU instruction..
MDR
Memory Data Register
- Holds the actual data or instructions.
- This may have been fetched from memory, or could be waiting to be written to memory.
Advantages of Embedded Systems
As they are dedicated to a single task, they are usually easier to design, cheaper to produce and more efficient at doing their task than a general purpose computer.
ALU
Arithmetic Logic Unit
- Does all the calculations
- Performs logic operations (AND, OR, NOT)
- Contains the accumulator register.
What is an Embedded System? +3 examples
Computers built into other devices. They are usually used for one function and are dedicated systems.
Examples include: dishwasher, DVD player, microwave
Clock Speed
The number of instructions a single processor core can carry out per second (Hz).
The higher the clock speed, the greater the number of instructions that can be carried out per second.
What is Secondary Storage
- Non-volatile
- Where all data (applications, operating systems and user tiles) are stored when not in use.
- Read/write speeds are much slower compared to primary storage.
HDDs (magnetic)
Hard Disk Drives
- Made up of a stack of magnetised metal disks spinning at a rate of between 5400 and 15000rpm
- Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disk.
- Portable HDDs are good for backing up and transporting lots of data.
Define Volatile
Temporary memory. It requires power to retain its data
Pros of Optical
Cheap
Portable
Quite durable
Cons of Optical
Low Capacity
Slow
Unreliable
