01-12-2012, 04:13 PM
Fundamentals of Computer Design
Fundamentals of Computer Design.ppt (Size: 841.5 KB / Downloads: 62)
Introduction
Old Conventional Wisdom: Power is free, Transistors expensive
New Conventional Wisdom: “Power wall” Power expensive, Xtors free (Can put more on chip than can afford to turn on)
Old CW: Sufficiently increasing Instruction Level Parallelism via compilers, innovation (Out-of-order, speculation, VLIW, …)
New CW: “ILP wall” law of diminishing returns on more HW for ILP
Old CW: Multiplies are slow, Memory access is fast
New CW: “Memory wall” Memory slow, multiplies fast (200 clock cycles to DRAM memory, 4 clocks for multiply)
Old CW: Uniprocessor performance 2X / 1.5 yrs
New CW: Power Wall + ILP Wall + Memory Wall = Brick Wall
Uniprocessor performance now 2X / 5(?) yrs
Sea change in chip design: multiple “cores” (2X processors per chip / ~ 2 years)
More simpler processors are more power efficient
Instruction Set Architecture: Critical Interface
Properties of a good abstraction
Lasts through many generations (portability)
Used in many different ways (generality)
Provides convenient functionality to higher levels
Permits an efficient implementation at lower levels
Instruction Set Architecture (ISA)
ISA is the actual programmer-visible instruction set.
Class of ISA;
Memory addressing;
Addressing modes;
Types and sizes of operands;
Operations;
Control flow instructions;
Encoding on ISA.
Performance Trends: Bandwidth over Latency
Bandwidth or throughput: the total amount of work done in a given time.
Such as megabyte per second for a disk transfer.
Latency or response time: the time between the start and the completion of an event.
Such as milliseconds for a disk access.