Книга: Distributed operating systems

6.2.1. On-Chip Memory

6.2.1. On-Chip Memory

Although most computers have an external memory, self-contained chips containing a CPU and all the memory also exist. Such chips are produced by the millions, and are widely used in cars, appliances, and even toys. In this design, the CPU portion of the chip has address and data lines that directly connect to the memory portion. Figure 6-1(a) shows a simplified diagram of such a chip.

Fig. 6-1. (a) A single-chip computer. (b) A hypothetical shared-memory multiprocessor.

One could imagine a simple extension of this chip to have multiple CPUs directly sharing the same memory, as shown in Fig. 6-1(b). While it is possible to construct a chip like this, it would be complicated, expensive, and highly unusual. An attempt to construct a one-chip multiprocessor this way, with, say, 100 CPUs directly accessing the same memory would be impossible for engineering reasons. A different approach to sharing memory is needed.

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