It is no longer necessary to develop one's own system. Times have changed greatly. Many systems now exist which work well and are worth copying. Manufacturers and suppliers are prepared to deliver entire systems assembled and ready to operate, complete with all the necessary system software and varying amounts of utility software. Although it may at first sight seem more economical to assemble a system within the laboratory, by use of laboratory personnel, in most cases it is now better to buy the system from a single supplier, completely installed and operable, saving one's own resources for matters more directly concerned with research. The costs in time and effort to develop a new computer system have been much larger than predicted, in almost every case known to the authors. Large laboratories having strong engineering staffs are an exception; outside of industrial plants they are the places where new system development and assembly makes the most sense.
2. Large-Scale Computations and Computing Centers
In general it is best to plan to do all very large-scale computing jobs (e.g., shell model and scattering theory calculations) at a large computing center and to set up in the laboratory a system which is just large enough to handle comfortably the data-acquisition jobs. Usually a medium-sized or small system will suffice. However, in some circumstances this will not be true.
3. Remote Large Computing Center On-Line for Data Acquisition
Direct transmission-line coupling to a large, remote computing center may prove practical for handling occasional low-priority bursts of data processing, for example, when one can be satisfied with guaranteed access within about 100 µsec, say, and a maximum guaranteed total access duration of no more than a few percent of any day. Such a hookup may also be valuable for the handling of data input and output in the remote batch mode of operation, especially if a card reader (or high-speed paper tape or storage device) and a line printer are available for this use, in the laboratory. However, there are few if any examples of successful high-priority prompt-interrupt operation. One should be extremely skeptical about the feasibility of relying on this last mode of operation.
4. Buying versus Renting
Rental rates have typically been set so that if the anticipated use period exceeds about three years, economic prudence suggests purchasing a computer rather than renting, providing that the necessary funds for capital investment are available. This can only be true, of course, because the life expectancy of modern computers is quite long, certainly over five years. (Also, one hesitates to trade in an old computer for which an excellent software collection exists!) The argument against renting standard peripherals is weaker, because they are electromechanical in nature and therefore have shorter lifetimes; furthermore, they tend to become outmoded. Renting can be especially attractive in special circumstances. For example, a line printer can be rented for the early period of operation of a system, while extensive program development work is in progress, and returned later, when the work has been finished.
5. New Computer or Current Model?
Computers are rapidly getting better and cheaper. This month's machine is much more powerful than last month's, dollar for dollar. New machines will always be appealing, but the prospective purchaser must balance their appeal against considerations of probable delivery date, software availability, completeness of documentation for both software and hardware, and in general the manufacturer's support capability. Unfortunately, these factors usually weigh against a new machine. As a rule, even a medium-sized system based on a new model machine will not be in full operation for approximately one year after delivery, unless both the hardware and the software have been tried and proven in a previous installation. On the other hand, in the case of an older model the same factors may all be favorable, but now the machine probably gives less computing per dollar, and the advantage of an early return on the investment must be weighed carefully against the likelihood of somewhat earlier obsolescence. At some time during the life of a computer the manufacturer will very likely cease to support its software and, usually later, its hardware.