Hello,

I assume that back-end pipe widths (issue, wb, commit and squash) are the
same. For a 2-way processor, an issue-width of 4 can be fine.

Regards,

--
Fernando A. Endo, Post-doc

INRIA Rennes-Bretagne Atlantique
France


2015-08-28 1:56 GMT+02:00 Rizwana Begum <[email protected]>:

> Hello All,
>
> I am trying to modify various width configurations in O3_ARM_v7a.py to
> simulate pipeline width of 2 (trying to model Cortex-A9). I modified the
> widths as follows:
>
> fetchWidth = 3 -> 2
> decodeWidth = 3 -> 2
> renameWidth = 3 -> 2
> dispatchWidth = 6 -> 2
> issueWidth = 8 -> 2
> wbWidth = 8 -> 2
> commitWidth = 8 -> 2
> squashWidth = 8 -> 2
>
> As I reduced the wbWidth, I ran into the following assertion failure
>
> gem5.opt: build/ARM/cpu/timebuf.hh:54: void TimeBuffer<T>::valid(int) const
> [with T = DefaultIEWDefaultCommit<O3CPUImpl>]: Assertion `idx >= -past &&
> idx <= future' failed.
>
> I changed the wbWidth, commitWidth and squashWidth back to 8 (its original
> value), as the effective width of the pipeline would still be 2 and my
> simulations were successful.
>
> I am curious if anyone has tried to modify the widths (specifically reduce
> the pipeline width). If so, what is the right way to determine and set
> write back and commit widths?
>
> Thank you,
> -Rizwana
>
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