Re: [Gems-users] Instruction Flow

[Luke Yen <lyen@xxxxxxxxxxx>]

Arrvindh,

   If I understand your question, you are asking about how Opal can
simulate executing speculatively without the use of MAI.

   Opal can do this because it is also a functional simulator that
is mostly correct in functional execution.  Opal fetches instructions from Simics through an
API call, which allows it to obtain an instruction given a PC value.  The
PC value can be updated speculatively through branch prediction (thus
affecting control flow).
Because Opal simulates an  OoO speculative processor it can still fetch
and execute (but of course not retire) instructions in speculative mode.

   Since every instruction is checked on retirement this allows Opal to
model the timing of an OoO processor but maintain the
functional correctness of the in-order Simics processor it is checking with.

   Luke

On Thu, 8 Sep 2005, arrvindh shriraman wrote:

> How does OPAL influence instruction flow in SIMICS if
> it does not use the MAI. Consider jmp instruction
> influenced by remote cache latency. The cache latency
> will influence the number of instructions executing
> speculatively.
>
> How does OPAL handle this ?
>
>
> Arrvindh Shriraman
> Conputer Science Department
> University of Rochester
>
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