LIMITED BY LIGHT

It turns out that microprocessor computer chips in the newest personal computers are spending most of their time waiting for light-limited communications with direct access memory. This limit also slows communications within the memory itself. As the requirements for memory access grow beyond the capabilities of cache memory on the processor, the main memory must move closer and closer to the processor. Gilder predicts that the entire memory and central processor will soon be forced onto the same chip. [As business advice he further predicts that the current manufacturers of memory will therefore take over the production of central processors (rather than vice versa) because the subsystem they are now making is larger than the central processor and so comprises most of the ultimate product.]

Moreover, another effect of this limitation is continued decentralization of information processing. The speed of light causes computers to remain physically small and limited in capability, so their distribution to hundreds of millions of separate locations around the world to meet local needs is more practical than centralized computers. Centralized computers are limited in capability by the light-determined size restriction and, also, by external communication rates.

A third effect that Gilder points out is in the nature of communications satellites. Geosynchronous satellites with rotation rates matched to the Earth's rotation are constrained by physics to be 23,000 miles above the Earth's surface. This causes a significant light-limited delay in communications with them. Low earth orbit satellites are placed, however, 60 times closer to the Earth's surface. Only a minor factor in current voice communications, the 60-fold decrease in communications delay has very great importance for digital computer-based communications. For this reason, extensive low earth orbit satellite systems are to be constructed. [As investment advice, he compares the companies engaged in this work.]

So, it is likely that, with current technology, computer processors and memory are going to merge in assemblies that become inexorably smaller; information processing will continue to decentralize to hundreds of millions of computers spread all over the earth; and these computers will talk to each other through fibre optic cables and a rotating shell of hundreds of satellites just a few hundred miles above the Earth's surface. The primary constraint determining this overall design is the unfortunate fundamental slowness of the speed of light, which moves at only 700 million miles per hour.