P4 Pipeline Registers

[Phoenix]

Well, I don't know a whole lot about P4 instructions, so I was wondering how the registers between each stage of the P4's 20 stage pipeline were. 20 stages is awfully long, and it seems that it might need some like a 200-bit register between each stage. Just curious.

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"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." - Albert Einstein

[Arcadian]

Originally posted by Phoenix:
Well, I don't know a whole lot about P4 instructions, so I was wondering how the registers between each stage of the P4's 20 stage pipeline were. 20 stages is awfully long, and it seems that it might need some like a 200-bit register between each stage. Just curious.

With 144 instructions simultaneously capable in flight, they would have to be much larger than that. I also imagine there to be a good amount of control bits that need to propogate between pipeline stages, especially those that control addressing of temperary buffers. I'm thinking you'll need at least over 500 bits in some of the larger stages.