Re: [Gems-users] IPC and Number of Instructions

[Dan Gibson <degibson@xxxxxxxx>]

The other processors are probably spinning. Spinning tends to have great IPC.

On Tue, Dec 8, 2009 at 2:53 PM, <ubaid001@xxxxxxx> wrote:

Hi all,

I simulated a four core CMP system with both Opal and Ruby. In the
results.opal file the runtime stats for processor [0],[1],[2],[3], only
processor [0] executed 100 million instructions specified by
"opal0.sim-step 100000000", but processor [1] and [2] have more total
number of instructions than what I had specified.

Even though only one core runs the required number of instructions, how do
the other cores run so many more instructions (almost double the number of
instructions specified). The configuration for all the processors are the
same. This leads to opal reporting a very high IPC for those processors.
e.g : P0 1.6, P1 3.96 , P2 3.97 etc.

This is due to the fact the the number of cycles remain the same for all
processors.

Am wondering if the high value of IPC reported is spurious. Can someone
shed more light on this?

Suhail




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