1.1 - Systems Architecture Flashcards
What is the function of the Program Counter (PC)?
To hold the address of the next instruction to be processed (fetched, decoded and executed) by the CPU
What is the function of the Memory Address Register (MAR)?
To hold the memory address of the current instruction (that is being processed by the CPU), and then the address of the data that it uses, so these can fetched from memory.
What is the function of the Memory Data Register (MDR)?
To hold the instruction that is being processed by the CPU, and the data (involved in the instruction) that has been fetched from memory.
What is the function of the Accumulator (ACC)?
To hold the result of an instruction before it is transferred to memory.
What is the role of Control Unit (CU)?
To coordinate and control all the activities taking place within the CPU; to decode and execute instructions; receive signals from system clock; direct timing and control of other parts of CPU
What is the function of the Arithmetic Logic Unit (ALU)?
To perform arithmetic calculations and logical operations.
What happens during the fetch stage of the fetch-decode-execute cycle?
Address of the instruction to be executed is copied from the PC to the MAR. Instruction at that address is fetched from memory and copied to the MDR.
What happens during the decode and execute stages of the fetch-decode-execute cycle?
The CU decodes the instructions and decides if data needs to be fetched. If so, MAR holds address of the data to be fetched. The data is fetched and stored in MDR.
What is a register?
A very fast memory location in the CPU that temporarily stores the data/instructions/addresses that are being used by the CPU.
What is cache memory?
A memory location in the CPU that provides fast access (faster access than RAM, but slower access than CPU registers) to the most frequently used programs and data.
What is meant by clock speed?
Number of cycles per second (Hz)
What is meant by the number of cores?
The number of duplicate processing units placed in one CPU.
How and why does increasing clock speed impact CPU performance?
Instructions in the CPU are processed on the pulse of the internal clock. So: quicker clock speed; faster the instructions are processed.
Why might increasing the number of cores increase CPU performance?
This allows for the potential to have several instructions performed per second.
Why might increasing the number of processors not increase CPU performance?
Software may not take full advantage of multiple cores, if they do not require multiple instructions to be processed at once.
