Module 4 Flashcards
What is a datapath
The set of functional units that carry out operations on a processor. These make up the CPU along with the ALUs and CUs.
The 1st pass of the datapath stores data and selects what components are used for the next set of instructions.
The 2nd pass gets data to the FU inputs and gets the old results from the FU outputs.
What are the ALU and CU
Arithmetic Logic Unit
- Does mathematics and floating point operations. Has inputs for data and the operands required.
Control Unit
- Directs the working of the CPU and tells which parts of the computer to respond during tasks
What is the ISA
The Instruction Set Architecture is the lowest level representation of the instructions available on some processor architecture. This decides the datapath and the control.
The ISA has the storage resources (instruction and data memory) and the datapaths required to execute them.
What are the two main Architecture Types
Harvard
- The storage of instructions and data are in separate areas
Von Neumann
- The storage of instructions and data are in the same place.
Harvard is preferred for ES use as it is a more robust and secure option.
What is the Decoder
Converts m-bit input to one of the 2^m bit outputs. This is used to decode instructions and chip select what is needed.
Basically sets the relevant outputs for some instruction to be carried out.
What is the Register
Stores values in a D Flip Flop. This is SRAM as the power has to remain on for instructions to be processed and the memory to be maintained.
What is the Multiplexer
Takes multiple inputs 2^m and connects it to the output line. Basically a slide switch that connects one of many input lines to a single output line. This is done based on which select line (or combination) is chosen.
What is the PCP?
The Peripheral Control Processor provides a means to transfer data across ports. It interfaces between instruction memory the other ports (USB, power, HDMI)
What is volatile memory and what are some types?
Memory that only holds it’s value when power is connected. Some examples include DRAM and SDRAM. DRAM is based on capacitors that leak over time and SDRAM runs with the system clock to do things.
What is non-volatile memory
ROM and EEPROM
ROM is highly robust and slower than the RAM. EEPROM is very slow to write but fast read. Flash memory is very high capacity and is programmed one block (8Kb) at a time. It is limited to about 100 000 read-write cycles.
What is a Digital Memory Unit
Memory cells that store binary data. Has data in and data out lines with address lines too.
What is a Memory Control Unit?
It manages interactions between the CPU and the external memory (DRAM, etc). This is done due to different speeds at which the processors and memory operate. Kind of like a gearbox.
Translates logic addresses
Allows for timing and controls to avoid resource conflict
Also allows for error detection
What is the typical memory hierarchy?
CPU -> Cache -> Main Memory -> Hard drive
As you go along the line, speed decreases but size increases. The CPU can only work directly within it’s own registers so work must be done to shift information from the different memory sources.
What is locality of referencing?
Temporal
- Time of access
Spatial
- Place of access in memory
A program has both of these localities - e.g. time required to run loops and the memory addresses access during.
Explain the use of the cache memory
The cache is the middleman between the CPU registers and main memory. Some of an instruction is left in cache and the rest must then be gathered from main memory.
L1 and L2 caches are the most common. L1 is the fastest and closest to the CPU. L2 connects the CPU to MM. L1 is on the processor and L2 is external as the ‘bridge’
