– What is limiting computer processors to operate beyond the current range of clock frequencies (from 3 to up 5GHz)?
In: Engineering
Depends on whether you’re speeding up something that exists or designing something new.
**Overclocking:**
When we talk about GHz we talk about a metric that is a combination of the CPUs multiplier and the front side bus speed of the motherboard it is currently slotted into.
With liquid hydrogen or other extreme cooling systems researchers have been slowly pushing their way to 9GHz. Increase your multiplier, speed up the FSB, push past stock voltage. This is overclocking.
Heat is a byproduct of the resistance of the components, they are not 100% efficiently conducting and so a portion of that electricity is expressed as heat. On the box the CPU will have a GHz rating and making it go faster than this starts with upping the voltage and ends with managing to keep it cool and stable.
**Processor Design:**
So what is a CPU? Let’s just say it’s a crazy amount of tiny switches called transistors. It has other parts, but nit relevant here. Small transistors still used today called MOSFETs were made in the 1950s. In the 1970s Gordon Moore predicted that the amount of transistors in ICs (read: computer chips) would double every 2 years as they got smaller and smaller.
Microprocessor engineers try to fit as much as they can in a given space. Most current gen CPUs have 3-4 billion transistors in them. When Moore noticed the trend, having a few thousand in a single IC was state of the art. The GraphCore Colossus MK2 has about 60 billion in a single IC, but it’s a damn sight larger than your desktop CPU.
So make switches smaller and you can put more in. We’re approaching a horizon where the laws of physics break down. That has to do with quantum mechanics but little to do with quantum computing. Can get into that if there’s interest but the short version that when me make them smaller than a given size, they stop working reliably.
There’s a physical gate speed limit (read: switches be switching) here that can be overcome with exponentially higher amounts of power, I’ll note that right around 2.8-3.2GHz there’s an increase in power necessary for most chips, so lots of reasons why core stacking is viable over a single faster core especially in mobile tech; but there’s also the distance that the electrical current will travel during one clock cycle – faster CPUs mean the power has less and less time to travel before the next clock cycle. Making faster CPUs means everything needs to be much smaller or closer, or else it’s not actually faster as it’s waiting for instructions. The speed of light is our limit here, so it’s very much an unbreakable barrier until someone proves otherwise.
Edit: bad grammar, spelling, i wasn’t totally awake.
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