CSC/ECE 506 Fall 2007/wiki1 1 11
Sections 1.1 and 1.1.2: Update performance trends in multiprocessors.
1.1 Why parallel architecture ?
The number of processors – new dimension to the design space. Demand: performance at acceptable cost Factors impacting performance gain
Microprocessor, minicomputer, mainframe, supercomputer – performance trend over time.
Single chip Microprocessor dominating – 1990s
Technological & architectural trends that strives to meet application demand for increased performance.
1.1.2 Technology trends
Scientific & engineering computing, Commercial computing
Difficult to wait for single processor to get fast enough Critical issues in parallel computer architecture are fundamentally similar to that in sequential computer: resource allocation among functional units, caches – locality, wires – communication bandwidth
1. Reduction in the basic VLSI feature size – makes transistor, gates, circuit faster & smaller – more fit in same area 2. Useful die size is growing – more area to use 3. Clock rate improves in proportion to size increase (1,2). Use of may transistors at once (parallelism) is expected.
Performance of microprocessor has been increasing at much greater rate than clock frequency. Benchmark for measuring workstation performance: SPEC, LINPACK Processors are getting faster in large part by making more effective use of an even larger volume of computing resources.
Basic single chip building block – 100 million transistors by year 2000. Raises possibility of placing more computer system on chip – including memory & I/O support. Possibility of placing multiple processors on chip. Evident commercially – system-on-a-chip: embedded systems
Memory technology: divergence between capacity & speed – capacity increased 1000 times, cycle time – factor of 2. Gap between processor cycle time & memory cycle time – wider. Memory bandwidth demanded by processor is growing rapidly. Latency: access time – One or two levels of caches on chip, additional level of external cache. Multiprocessor design – how to organize collection of caches.
Disks: Parallel disk storage system – RAID – norm. Large multilevel caches for files / disk blocks are predominant.