QS Flashcards
What is an instruction set
The instruction set, also called ISA (instruction set architecture), is part of a computer that pertains to programming, which is more or less machine language. The instruction set provides commands to the processor, to tell it what it needs to do. The instruction set consists of addressing modes, instructions, native data types, registers, memory architecture, interrupt, and exception handling, and external I/O.
An example of an instruction set is the x86 instruction set, which is common to find on computers today.
What is the difference between a 16-bit, 32-bit and 64-bit computer
n computing, 32-bit and 64-bit are two different types of processors. The bit number (usually 8, 16, 32, or 64) refers to how much memory a processor can access from the CPU register.
) Computer X which has 16 address lines, 8 data lines & L1 cache (32 bytes) and block
size of 8 bytes. It also contains 8085 microprocessor.
Computer X is a 16-bit computer. True or False? Briefly explain your answer
(3 marks)
KL
Describe CISC architecture
A complex instruction set computer (CISC /ˈsɪsk/) is a computer architecture in which single instructions can execute several low-level operations (such as a load from memory, an arithmetic operation, and a memory store) or are capable of multi-step operations or addressing modes within single instructions.
Describe RISC architecture
A Reduced Instruction Set Computer is a type of microprocessor architecture that utilizes a small, highly-optimized set of instructions rather than the highly-specialized set of instructions typically found in other architectures.
STATE and EXPLAIN any THREE differences between CISC & RISC architecture
RISC vs CISC
Emphasis on software- Emphasis on hardware
Small number of fixed length instructions- Large number of instructions
Simple, standardised instructions- Complex, variable-length instructions
Single clock cycle instructions- Instructions can take several clock cycles
Heavy use of RAM- More efficient use of RAM
Low cycles per second with large code sizes- Small code sizes with high cycles per second
Advantages of RISC
The performance of RISC processors is often two to four times than that of CISC processors because of simplified instruction set.
This architecture uses less chip space due to reduced instruction set. This makes to place extra functions like floating point arithmetic units or memory management units on the same chip.
The per-chip cost is reduced by this architecture that uses smaller chips consisting of more components on a single silicon wafer.
RISC processors can be designed more quickly than CISC processors due to its simple architecture.
The execution of instructions in RISC processors is high due to the use of many registers for holding and passing the instructions as compared to CISC processors.
Advantages of CISC
Microprogramming is easy to implement and much less expensive than hard wiring a control unit.
It is easy to add new commands into the chip without changing the structure of the instruction set as the architecture uses general-purpose hardware to carry out commands.
This architecture makes the efficient use of main memory since the complexity (or more capability) of instruction allows to use less number of instructions to achieve a given task.
The compiler need not be very complicated, as the micro program instruction sets can be written to match the constructs of high level languages
What are the main characteristics of RISC
processors?
Simpler instruction, hence simple instruction decoding.
Instruction comes undersize of one word.
Instruction takes a single clock cycle to get executed.
More general-purpose registers.
Simple Addressing Modes.
Fewer Data types.
A pipeline can be achieved.
What are the main characteristics of CISC
processors?
Complex instruction, hence complex instruction decoding.
Instructions are larger than one-word size.
Instruction may take more than a single clock cycle to get executed.
Less number of general-purpose registers as operations get performed in memory itself.
Complex Addressing Modes.
More Data types.
Explain what is a WAIT state
A wait state is a situation in which a computer program or processor is waiting for the completion of some event before resuming activity. A program or process in a wait state is inactive for the duration of the wait state.
Describe the stored program concept when applied to the Von Neumann model
The idea was introduced in the late 1940s by John von Neumann, who proposed that a program be electronically stored in binary-number format in a memory device so that instructions could be modified by the computer as determined by intermediate computational results.
Give two different reasons why increasing the die (chip) size of a microprocessor increases the cost of the microprocessor. Recall that dice (chips) are tiled on a wafer for fabrication
Turning silicon into chips is expensive, and that cost is roughly proportional to the surface area of the silicon (assuming the same process generation). Double the area of the die and you double the cost to make it.
The bigger the CPU, the less yield they get from the silicon, and not all silicon is made equal. Minor imperfections occur in the process, and a number of chips are tossed out right from the get go due to unavoidable defects during manufacture. The larger you go, the more likely a given chip will have a defect that affects its performance, or makes it unusable.
In the 8085 microprocessor, what is the function of the program counter (PC)?
The function of the program counter is to point to the memory address from which the next byte is to be fetched. When a byte (machine code) is being fetched, the program counter is incremented by one to point to the next memory location.
What is the relationship between threads and processes?
A process defines an address space and dynamic resource ownership. Multiple threads may be created and executed within that process.
