Processor Trends and I/O Device Rates

Typical I/O Device Data Rates

• Input/Output (I/O) devices vary in data rate (bits per second or bps)
• For example, Ethernet modems can have a data rate of up to 10^9 bps, while graphics displays can have rates of 10^6 bps.

Improvements in Chip Organization and Architecture

• Shrinking logic gate size on processor chips leads to more gates packed tightly, increasing clock rate and reducing signal propagation time.
• Dedicated cache memory on the processor chip reduces cache access times.
• Changes in processor organization increase effective instruction execution speed through parallelism.

Problems with Clock Speed and Logic Density

• Power density increases with denser logic and higher clock speeds, posing a challenge for heat dissipation.
• Resistance and capacitance of metal wires connecting logic gates limit electron flow, leading to increased delay as components shrink.
• Memory access speed and transfer speed lag behind processor speeds.

Processor Trends from 1970 to 2010

• Significant increases in transistors, frequency, power, and cores over time.

System Performance Evaluation

• Benchmark suites are collections of representative programs used to evaluate computer systems for specific applications.
• SPEC, an industry consortium, develops and maintains benchmark suites for evaluating computer systems.
• Performance measurements from these suites are used for comparison and research.

SPEC CPU2017

• A widely used benchmark suite for processor-intensive applications.
• Consists of integer and floating-point benchmarks designed to evaluate computational performance.
• Includes benchmarks for various applications like Perl interpreter, compiler, route planning, network simulation, and video compression.

Terminology Used in SPEC Documentation

• "Benchmark": A program designed to test system performance.
• "Peak metric": Performance optimization for compiler output.
• "Speed metric": Time taken to execute a benchmark, measuring single task completion.
• "Rate metric": Amount of work completed per unit time, quantifying throughput or capacity.

SPEC Evaluation Flowchart

• Benchmark programs are run three times, with the median value selected.
• Ratio is calculated as Tref(prog) / TSUT(prog), where Tref is the reference time and TSUT is the system under test time.
• Geometric mean of all ratios is computed to determine the system's overall performance.

Program Timing with Long I/O Wait

• Without interrupts, the processor waits during I/O operations, leading to inefficient use of processing time.
• With interrupts, I/O operations can occur concurrently with processing, maximizing system utilization.

Communication Pathways: Buses

• A bus is a shared transmission medium connecting multiple devices.
• Signals from one device are accessible to all other devices connected to the bus.
• Multiple communication lines exist within a bus, each carrying signals representing binary 0 and 1.
• Computer systems have various buses connecting components at different levels of the system hierarchy.

System Bus

• Connects major components like the processor, memory, and I/O.
• Key interconnection structure in computer systems.

Data Bus

• Provides a path for moving data between system modules.
• Consists of multiple data lines, determining the width of the data bus.
• Wider data buses allow for more bits to be transferred simultaneously, leading to improved system performance.

Explore the advancements in chip organization and architecture, including I/O device data rates and challenges related to clock speed and logic density. Understand the implications of these trends on processor performance and efficiency.