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Comment by teej | Hacker News Reader

It seems that the complexity of the technology is already out of immediate reach for hardware hackers of this sort. This is an 8-bit cpu!

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Well just build two and you got a 16-bit'er and so on. Bit size it really not much more than linear scaling. Other things like pipe-lining are behind the complexity of modern cpus.

Two 8-bit cores != a 16-bit CPU.

By your math, every dual-core 64-bit Intel CPU would actually be a 128-bit processor, a quad-core would equate to a 256-bit system, and the Cell would be a very studly 1088-bit chip (64-bit PPE + 8x128-bit SPEs).

You appear to be confusing "linear" scaling with "exponential", which makes a serious difference.

It's in principle pretty simple to interconnect two n-bit CPUs and obtain one 2n-bit CPU. The only element that scales above linear is the multiplier, and it's not even quadratic.

True, depending on what you mean by "bit". I'm not sure it is entirely trivial to interconnect the instruction-parsing parts, and memory operations might also be interesting. The ALU would be pretty simple, but you'd lose a lot of speed there (assuming something else didn't kill you first), as even if you have two CLA's (seems unlikely, given the additional complexity), you'd double the time it would take to stabilize the outputs.

My point is, that just characterizing a CPU by saying it's an n-bit architecture, doesn't say very much about the complexity of the real thing.

You should not fall prey to the (in other contexts appropriate) assumption that an increase of one bit inherently doubles complexity (confusing linear with exponential).

That's why the Atari Jaguar is 64-bit. DO THE MATH.

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