Response time is one of the most important performance measures associated with a typical multi-user system. Response time, in turn, is bounded by the performance of the input/output (I/O) subsystem. Other than the end user and some external peripherals, the slowest component of the I/O subsystem is the disk drive. One standard strategy for improving I/O subsystem performance uses high-performance hardware like Small Computer Systems Interface (SCSI) drives to improve overall response time. SCSI hardware, unfortunately, is often too expensive to use in low-end multi-user systems. The low-end multi-user systems commonly use inexpensive Integrated Drive Electronics (IDE) disk drives to keep overall costs low. On such IDE based multi-user systems, reducing the Central Processing Unit (CPU) overhead associated with disk I/O is critical to system responsiveness. This thesis explores the impact of PCI bus mastering Direct Memory Access (DMA) on the performance of systems with IDE drives. DMA is a data transfer protocol that allows data to be sent directly from an attached device to a computer system’s main memory, thereby reducing CPU overhead. PCI bus mastering allows modern IDE disk controllers to manipulate main memory without utilizing motherboard-resident DMA controllers. Using a series of experiments, this thesis examines the impact of PCI bus mastering DMA on IDE performance for synchronous I/O, relative to Programmed Input/Output (PIO) and SCSI performance. Experiment results show that PCI bus mastering DMA, when used properly, improves the responsiveness and throughput of IDE drives by as much as a factor of seven. The magnitude of this improvement shows the importance of operating system support for DMA in low-end multi-user systems. Additionally, experimental results demonstrate that performance gains associated with SCSI are dependent on system usage and operating system support for advanced SCSI capabilities. Therefore, under many circumstances, high-performance SCSI drives are not cost effective when compared with IDE bus mastering DMA capable drives.

International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / Due to the vast amount of data required to be collected for design/performance analysis of operational and development systems, there has evolved a real requirement for a high-speed, large capacity, data collection/record system in a small Flight/Ruggedized package. This need is realized by several user communities and factors which include the evolution of small operational vehicles (airborne, land and UAV’s), the desire of weapons manufacturers/integrators to be independent from the vehicle during vehicle integration, and a general need for a field/airborne, reliable portable data collection system for intelligence gathering, operational performance verification and on-board data processing. In the Air Defence community, the need for a ruggedized record system was highlighted after Desert Storm, in which the operational performance of the Patriot Missile was questioned and data collection was not performed to support the performance. The Aydin Vector Division in conjunction with the prime contractor, has come up with a solution to this problem which utilizes a commercially available helical scan 8mm data storage unit. This solution provides a highly reliable record system, ruggedized for airborne and field environments and a low price in comparison with the more traditional approaches currently offered. This paper will describe the design implementation of this small ruggedized, flight worthy Data collection system deemed the ATD-800. It will also discuss the performance and limitations of implementing such a system, as well as provide several applications and solutions to different operational environments to be encountered. Additionally, the paper will conclude with several product enhancements which may benefit the flight test, operational and intelligence communities in the future.