Why Are We Still Using Multi-core Processors Instead of Stronger Single-core Ones?

You may have noticed that despite all the current advancements in our computing technology, the clock speeds of our chips haven’t really increased in the last few years. Instead, our computers now run with multi-core processors that channel all the different tasks on separate chips, so why are we not just building stronger single-core processors that handle everything in one place?

The reason for that is that the process of transmitting data between memory and chip can’t seem to keep up with higher clock speeds. Basically, electrons are simply not fast enough to interconnect between the memory and processors with higher clock speeds, this is known as the Von Neumann Bottleneck.

The problem here is that in order to increase clock speed, the silicon transistors on the chip must be able to switch faster. This requires higher input voltages that result in greater leakage (power that passes through the circuits without doing anything useful, essentially lost power). This means that the power consumption as well as the heat output of the processor increase significantly.

As a practical example of how a small difference in a processor’s speed can significantly affect the power required to run a processor, Intel’s E5640 Xeon processor (4 cores, 2.66 GHz) has a power envelop of 95 watts, the L5630 (4 cores, 2.13 GHz) however requires only 40 watts. That’s only 24% more CPU power at the cost of 137% more electrical power required. The X5677 on the other hand, has a speed of 3.46 GHz, that’s 60% more processing power for 225% more electrical power.

So what are the alternatives?

In order to get over the limiting powers of current electrons, scientists are looking to replace them with photons of light. Meaning that if we manage to replace the electrical interconnects of a computer with something optical, information could be sent between memory and processor at the speed of light. Only then would there be no trouble in transmission keeping up with the speed of computation.

But this approach comes with its own set of obstacles however, if we only replace the interconnects (or method of communication) between the memory and the processor with light, there would still be an issue of switching between electrons and photons at either end. The only way to get around that it seems, is if we manage to build a computer that runs solely on optical power, with the memory and processor operating with light rather than electricity, a problem which scientists have finally cracked at least part of.

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