Re: What is a scoreboard?

/* Written 9:00 am Dec 18, 1987 by johnl@ima.UUCP in convex:comp.compilers */
In article <797@ima.ISC.COM>, ...!harvard!talcott!motcoh!mark writes:
> Can someone explain the technique of using "scoreboards" in
> compiler development? Any references?


        I don't have any hard references, but when I ran into the CDC 6600
hardware it was described as having a hardware scoreboard. With regard
to compilers, it comes up with some of the RISC designs, where the
compiler has to do instruction scheduling and branch delays. I would
imagine that is where the term came from.


        A scoreboard keeps track of the various functional units of the
machine, and will not allow access to a unit, until it finishes. For
example, if divide takes 8 clock units, a scoreboard would indicate that
the any reference within the 8 clock units to either the input and
result registers would pend instructions. Even if the hardware provides
such a scoreboard, on such machines it is usually an advantage to have
the compiler know about these delays, so that it can try to do more
stuff in parallel.
--
Michael Meissner, Data General. Uucp: ...!mcnc!rti!xyzzy!meissner
Arpa/Csnet: meissner@dg-rtp.DG.COM
--

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