[libre-riscv-dev] [hw-dev] Re: 6600-style out-of-order scoreboard designs (ariane)

[Luke Kenneth Casson Leighton]

Let me put it another way.

* the FU Regs global read write vectors, because they are tested
unconditionally against the FU reg unary numbers, generate BOTH a read
hazard AND a write hazard in that loop case.

* the FUFU matrix however had the 1st instruction trigger to capture the
read relationship in one of its cells.

BUT

* because the Issue signal is on the X of the FU FU matrix (and GORD/WR on
the Y), the 2nd instruction captures the write relationship in a COMPLETELY
different cell.

* in the case of the ADD  R4 R4 R7   ADD R7 R7 R4 example, the  FUFU Matrix
will capture the RD relationship in FUFU cell 2,3 for example and the write
relationship in FUFU cell 3,2.

The FUREGs matrix alone can NOT capture this vital information.

L.



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