Microcomputer Systems Using the STE Bus

It has been shown that a modular bus system is an ideal configuration for constructing a computer to help solve a problem: those devices which are best suited to the problem are plugged into the bus, just as the appropriate instructions are selected. The description ‘devices’ includes not only memory and peripherals, but also the microprocessor. The devices need to be connected together, but there is no standardisation between manufacturers as to the signals required for the connection; hence a number of bus systems have been proposed. Some systems were designed by the manufacturers and so are based around their own products, which can make connecting other devices to these buses problematic. Other systems were proposed by independent bodies with the requirement that any device could be connected easily, regardless of manufacturer or product: these systems are described as processor independent. Some of the proposals have been adopted formally by bodies such as the IEEE: the advantage of these is that a standard is provided to which designers adhere. Where this has not occurred, there tend to be variations in the standard, making it awkward to connect devices from different manufacturers.

For a computer system to work correctly, both the hardware and the software must be right. Unfortunately, it is impossible to guarantee that both parts will be correct: the hardware may be at fault, or the software. Certainly the software can be in error: a computer does exactly what it is told and not necessarily what you thought you told it to do. The hardware may have been designed incorrectly, an error may have occurred during construction, or one of the components may be damaged. Thus when a system is first configured and it does not work (which happens all too often), is it the software that is wrong, or is the hardware faulty?