07-05-2012, 11:16 AM
COMPUTER ARCHITECTURE and ORGANIZATION STUDY PROJECT
COMPUTER ARCHITECTURE & ORGANIZATION STUDY PROJECT.pptx (Size: 104.88 KB / Downloads: 35)
Introduction
ARM is a 32 bit RISC processor architecture currently being developed by the ARM corporation. ARM processors possess a unique combination of features that makes it the most popular embedded architecture today.
ARM cores are very simple which means that they are manufactured using a comparatively small number of transistors,leaving plenty of space on the chip for application-specific macrocells.
both ARM ISA and pipeline design are aimed at minimising energy consumption.
the ARM architecture is highly modular: the only mandatory component the integer pipeline.thus making it highly efficient.
ARM ISA Overview
The classical RISC approach requires the execution stage of any instruction to complete in one cycle. This is essential for building a pipeline. While most ARM data processing instructions do complete in one cycle, data transfer instructions are one important exception. Completing a simple store or load instruction in one cycle would require performing two memory accesses in a single cycle: one -to fetch the next instruction from memory, and the other - to perform the actual data transfer However, in order to achieve better utilisation of the pipeline during 2-cycle instruction executions, they introduced an auto-indexing addressing mode, where the value of an index register is incremented or decremented while a load or store is in progress.
Evolution of the ARM Pipeline
The 3-stage pipeline
fetch – decode – execute.(process->reads instruction,
load & store instruction takes two cycle per instruction.
stall takes whenever complex instruction comes.
The 5-stage pipeline –
1st operation – two way for operation & load-store.
Merging of read & decode
3 stages of execution-first stage performs arithmetic computations, the second stage performs memory accesses (this stage remains idle when executing data processing instructions) and the third stage writes the results back to the register file.
Conclusion
There is still considerable controversy among experts about which architecture is better. Some say that RISC is cheaper and faster and therefore the architecture of the future.
RISC has now existed more than 10 years and hasn't been able to kick CISC out of the market. If we forget about the embedded market and mainly look at the market for PC's, workstations and servers I guess a least 75% of the processors are based on the CISC architecture.
Yet the 601 is considered a RISC chip, while the Pentium is definitely CISC. Furthermore today's CISC chips use many techniques formerly associated with RISC chips.