this post was submitted on 23 Jun 2024
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[–] [email protected] 142 points 5 days ago* (last edited 5 days ago) (20 children)

We do, depending on how you count it.

There's two major widths in a processor. The data register width and the address bus width, but even that is not the whole story. If you go back to a processor like the 68000, the classic 16-bit processor, it has:

  • 32-bit data registers
  • 16- bit ALU
  • 16-bit data bus
  • 32-bit address registers
  • 24-bit address bus

Some people called it a 16/32 bit processor, but really it was the 16-bit ALU that classified it as 16-bits.

If you look at a Zen 4 core it has:

  • 64-bit data registers
  • 512-bit AVX data registers
  • 6 x 64-bit integer ALUs
  • 4 x 256-bit AVX ALUs
  • 2 x 128-bit data bus to DDR5 (dual edge 64-bit)
  • ~40-bits of addressable physical RAM

So, what do you want to call this processor?

64-bit (integer width), 128-bit (physical data bus width), 256-bit (widest ALU) or 512-bit (widest register width)? Do you want to multiply those numbers up by the number of ALUs in a core? ...by the number of cores on a piece of silicon?

Me, I'd say Zen4 was a 256-bit core, but you could argue any of the above numbers.

Basically, it's a measurement that lost all meaning so people stopped using it.

[–] [email protected] 5 points 4 days ago (3 children)

I'm surprised some marketing genius at the intel/amd hasnt started using the bigger numbers

[–] [email protected] 5 points 4 days ago (1 children)

I expect the engineers are telling the marketing people "No! You can't do that. You'll scare everyone that it's incompatible."

[–] [email protected] 1 points 3 days ago (1 children)

32bits is compatible with 64bits, why wouldn't 128 bits be too?

[–] Peffse 1 points 3 days ago

64bit cut out 16bit compatibility. So I'm guessing the fear is that 128 would cut 32.

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