Comp2- Machine architecture Flashcards
Which unit in the processor does calculations and whats it made of?
Arithmetic logic unit
made of circuits.
What calculations does the arithmetic logic unit do? (5)
adding, subtraction, fixed point and floating point arithmetic, Boolean logic, shift operations.
What does the program control unit do.
fetches program instructions from memory, decodes them and executes them one at a time.
Whats in the program control unit?
Instruction decoder, Program counter, Current instruction register , control circuits and the status register.
What are registers?
fast memory locations inside the processor(or I/O controller) they can be dedicated or general purpose.
How are general purpose registers accessed?
through instructions such as LOAD,STORE and ADD.
What does the stack point (SP) dedicated register do?
points to a stack holding return addresses, procedure or function parameters, and local variables, accessed when a procedure or function is called.
What does the program counter (PC) dedicated register do?
points to the next instruction to be fetched and executed.
What does the status register (SR) dedicated register do?
Holds conditional codes to indicate the outcome of operations. eg sign,zero, overflow,carry flags are set accordingly . (a series of bits, one for each flag.)
What does the accumulator (ACC) dedicated register do?
holds the result of the current set of calculations, eg ADD #36 , adds 36 to the contents of the accumulator.
how are general purpose registers labeled?
R0, R1, etc
What does the current instruction register(CIR) do/hold?
holds the current instruction to be executed while it is decoded and executed.
What does the memory address register(MAR) do/hold?
holds the address of the memory location currently being accessed by the processor.
What does the memory buffer register(MBR) do/hold?
holds the data item being transferred to or from the memory location currently being accessed.
what is a general purpose register?
a register not assigned a specific role by the processor designer, programmers may use them.
what is a dedicated register?
a register assigned a specific role by the processor designer. programmers may use some but not all dedicated registers.
What does the clock do?
each cycle of it triggers one step in the fetch execute cycle.
what do the control circuits do?
send the control signals down the control bus, eg read , write.
How does clock speed effect performance?
A higher clock speed means more instructions can be fetched and executed every second.
how does word length effect performance
the bigger the word length , the bigger the operands results can be accommodate. if the result exceeds the word length extra processing must be done to split operands and results across different registers which slows it down.
word length in the MAR and PC effects how much addressable memory there is.
what is clock speed
the clock speed of a processor is the frequency in MHz or GHz at which the processor executes instructions.
what is word length
The number of digits in a binary word.
what is bus width
The number of signal wires/ lines allocated to a bus.
how does memory bus width effect performance
More addressable memory.
how does data bus width effect performance
More bits of data can be transferred along the bus in one go which should improve performance as less cycles have to happen to transfer the same amount of data.
What is a multicore processor and how does it effect performance?
More then one microprocessor on the same chip. with multiple cores (processors) multiple tasks can be run at once or a single task can be split among many cores.
What is cache memory and how does it improve performance?
Cache memory is a small amount of very fast SRAM located near/on the processor core. When a memory location is accessed a whole chunk of nearby data is loaded into the cache, it takes advantage that the next bits needed are in the next memory addresses.
What is pipelineing?
While one instruction is being executed the next is being fetched.
how does instruction set improve performance?
Using more complex instructions means less instructions need to be run which means less FE cycles. more instructions mans more bits need to be used for the op-code.
why is their a limit on clock speed?
At a faster speed increases heat which becomes a big problem at high frequencies because the heat cant be removed quick enough.
Define instruction set.
The set of bit patterns or binary code for the machine operators that a processor has been designed to perform.
What is the op-code?
The part of the machine code instruction that denotes the machine code operation eg ADD
what is a operand?
The part of the machine code instruction that represents a single item of binary data or the address of a single item of binary data.
Steps of the fetch execute cycle using register transfer notation?
MAR
How do you increase processing power? (4)
Multi core processor
increased cache size
pipelining
More complex instruction set
Define microprocessor
CPU but dosnt include the memory its just the processing part of the chip.
Whats the stored program concept?
A program must be in the main memory to be executed, it is processed by fetching machine code instructions in SEQUENCE from main memory and executing them, ONE AT A TIME, in the processor.
Define hardware.
Electronic/electrical circuits that a computer is assembled from.
Define main memory.
memory that can be directly addressed by the processor.
What is the von neuman spc?
single storage system - for data +programs
2 clock cycles per instruction
gets instruction first then data.
same bus for both.
What is the Harvard spc?
two memories- one data , one program
1 clock cycle per instruction
separate buses for each
this is better as both things happen at once without competing against each other.
What is the main memory mad eof and what does it store?
RAM, software(programs) +data
What is RAM?
Random Access Memory.
volatile-memory lost when no power.
Faster then ROM at reading
can be accessed at any time, or order from any location.
What is ROM?
Read Only Memory
non-volatile
can be accessed randomly like RAM but cant be easily altered(written to) so its used to store fixed programs such as a pc’s bootstrap program.
Whats is PROM?
Programmable Read Only Memory
can be edited using high voltage.
What is EPROM?
Erasable Programmable Read Only Memory
can be edited with UV radiation
what is EEPROM(like flash)
Electronically Erasable Programmable Read Only Memory
can be edited by a normal pc, but this takes longer then reading.
Whats the difference between SRAM and DRAM?
SRAM-static RAM - has more capacity
DRAM- dynamic ram - needs more refreshing -slower.
two types of flash.
NAND type- can rewrite certain parts
NOR type- can rewire certain bytes
what is flash?
modern EEPROM- fast to erase and rewrite by the computer, is shock resistant its used in phones , cameras etc.
Addressable memory?
memory that can be directly addressed by the processor.
what is a peripheral
a computer device that is not part of the cpu, it can be external eq mouse or internal eg cd ROM-drive.
What does an I/O controller do?
As the processor cant be designed to work with every peripheral, due to different components, clock speeds and voltages. the I/O controller relays the data and instructions to and from the peripheral.
It provides the correct voltages and currents for the system bus and I/O device
What 3 parts are in a I/O controller?
electronics that interface the controller to the system bus
data,
command and status registers
electronics for sending contol signals to connected devices
what is the I/O port?
Part of the I/O controller. It is a set of data command and status registers.
it allows exchange of data from the processor to the peripheral.(either one way or 2)
what is secondary storage?
permanent storage memory, not directly connected to the processor, also called backing store. eq magnetic disk drive.
what is a I/O device?
a hardware unit that sends or receives data or stores data by communication with the processor/main memory through the I/O controller.
Whats the system bus or external bus?
the main highway connecting the processor, main memory, and I/O controllers; it is made of the data bus, address bus, and control bus.
What is the data bus?
bidirectional
typically 32 wires
transports data between the three main components.
what is the control bus?
bidirectional
typically 8 wires
transports control signal between the three main components.
eq; clock signal, reset signal, check memory read, check memory write, I/O is being addressed not memory?
what is the address bus?
unidirectional
typically 32 wires
used to address memory and I/O locations.
what is parallel connection is buses.
multiple wires are used to transmit the info.
what is the only component that feeds to the address bus?
the processor
what controls can go along the control wire?(5)
clock signal-for timing
reset signal- to initialize components
memory read- to say the memory is being read from
memory write -to say the memory is being written to
I/O: to indicate to use I/O not main memory if they both have the same memory address.
what is a Microcontroller?
A complete computer on a single chip. (processor, memory, and I/O)
ued in devises such as mp3 players, where few instructions are needed.
what are the two addressing modes?
Immediate mode
Direct mode
what is immediate addressing mode?
The value you want to process is a fixed value(operand) eg ADD #6 , addes 6 to the accumulator
what is direct addressing mode?
The address of the value you want to process is supplied (operand) eg ADD 6 , addes contents of memory address 6 to the accumulator.
