Interfacing Laboratory Instruments to Multiuser, Virtual Memory Computers

Abstract

Computers based on virtual memory. multiuser architecture have recently become economically available to medium sized research groups (about 25 members). These new computers offer advantages to the experimentalist. though acceptance has been sometimes limited. One of the most important advantages of a virtual memory machine is the capability of fast access to arrays having dimensions greater than 64 kbytes. Arrays larger than 64 kbytes were available on some older computers based on physical memory. The access time to the memory beyond 64 kbytes is extremely slow for these systems. Fast access to large arrays is particularly important now where large data sets are required for research systems.Many researchers are accustomed to a dedicated computer running a single-user operating and data acquisition system. When there are several experimentalists in a research group. the advantage of a multiuser system becomes important. The resources a computer provides can be shared among the users at a much lower cost than that of maintaining a separate dedicated computer and peripherals for each project. Software routines for instrument control and data acquisition as well as data bases are sharable resources. Expensive hardware resources. such as array processors. images processors. terminals. printers and color plotters can also be shared.There are difficulties in assembling the hardware and software facilities required for a multiuser. experimental research oriented system. The single-user operating systems typically use built-in commands for easy instrument communication and other functions well suited for the experimenter's needs. A multiuser computer's input-output capabilities are more powerful but harder to understand. The user is left with the responsibility for bridging the gap between the capabilities provided and his particular needs for data acquisition and communication with devices.