Thanks for your answer, 

Does that means for results for papers and for comparing with real systems 
should I use a "detailed" cpu?
My problem is that the simulation with detailed CPU for the spec2006 takes 
weeks, for complete execution and ref inputs.
Rodrigo

Date: Thu, 28 Feb 2013 17:56:37 -0600
From: [email protected]
To: [email protected]
Subject: Re: [gem5-users] IPC

By using the "timing" cpu, you are effectively using something that is like an 
idealized 1-wide, in-order cpu model.  So the maximum possible IPC would be one 
and with cache accesses, etc it should be expected to be much lower than one.

For relative comparisons, especially papers not looking explicitly at core 
architecture, it's probably ok.  Be aware that compared to an out of order cpu 
model, in-order cpu models have no way of overlapping/hiding memory latency 
with other useful work (like in the shadow of a miss to an L2 cache).  So the 
relative performance differences vs an out of order cpu model may be skewed.


On Thu, Feb 28, 2013 at 5:46 PM, Rodrigo Reynolds Ramírez 
<[email protected]> wrote:





Hello everyone,
I am working with cache replacement policies and I want to compare the IPC 
between these algorithms, I am using a --cpu-type=timing. For comparing the 
performance I am using the IPC, I am calculating it as 
system.cpu.committedInsts/system.cpu.numCycles, but the values I got are 
different from papers and the ones I got from other simulator.

The timing model is valid for calculating the IPC?I have read in the forum some 
people talking about low IPC for h264, actually all my spec2006 benchmarks have 
a low IPC.

Thanks in advance                                 Rodrigo                       
                  

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