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Comment by lbriner | Hacker News Reader

So a "modern" CPU to the same scale would be around 20 acres. Hmm, I'll start saving up now.

And probably not faster either, considering that the thing runs at 60 kHz due to its size.

A 20 acre square is about 925ft to a side.

Speed of light is really starting to matter. That's about a nanosecond just for signal to propogate, and that's assuming a straight wire with no intermediate components.

925 feet is around 940ns assuming speed of light in a vacuum. Speed of light in copper traces is slower.

> Speed of light in copper traces is slower.

Approximately 0m/s over any practical distance. :)

I should imagine capacitance and inductance are going to hit the clock speed waaaay before theoretical speed of light barrier comes into play.

There were some pretty serious limitations on parallel buses and backplane designs back in the day. Hence everything went serial (USB, PCIe, etc).

The speed of light often seems so fast as to be infinite, or at least hard to comprehend, in daily life. I was surprised the first time I calculated the minimum possible round trip time from New York to San Francisco, as the crow flies: it's just under 28ms not counting any overhead whatsoever from switching, electronics, etc. It amazes me that an actual network ping is only about double that, considering all the overhead of switching, and that light doesn't travel at full speed in fiber optic cables.

No kidding, high speed traders are spending big bucks on getting an advantage over fiber networks by using microwave links spanning continents[1]

[1]: https://arstechnica.com/information-technology/2016/11/priva...

I worked on an algorithmic trade platform for an options broker/market maker. We bought rack space next to the ISE exchange's racks, which comes at a premium over rack space ACROSS THE ROOM.

It's a problem in mobile comms too. There's a concept called timing advance: in order for TDMA frames to arrive in the correct time slot and not crap all over the neighbouring frames from other users, they have to be sent earlier by the handset, depending on the distance from the base station.

(At least it's not GPS where the orbit speed plus lack of gravity means you have to factor relativity into the mix too!)

One of the best demos I remember from university, was on the first day of a digital logic class. The professor passed out a bunch of short pieces of yarn, then proceeded to explain that they were the length of a clock cycle in a typical CPU.

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