[Eda-dev] Experiment with gscl45nm with Verilog output from an LRU implemented in Chisel

Øyvind Harboe oyvind.harboe at zylin.com
Thu Jul 11 08:49:01 EDT 2019


Thanks for the explanation.

If I understand you correctly: the 1.9ns is the correct and expected setup
time for gscl45nm that I'm reproducing with the 560MHz result. It merits
further investigation, but best as we know currently 560MHz seems to be in
the right neighborhood for gscl45nm for the LRU.v example.

I'm sure you already explained this to me, but there's a lot of information
and moving parts when testing out qflow for me and I missed your
explanation.

With the Dockerfile setup, it is repeatable, I ran it twice: 560MHz both
times.




On Thu, Jul 11, 2019 at 2:39 PM Tim Edwards <tim at efabless.com> wrote:

> Hello Øyvind,
>
> > Did something change recently that improved fMax for the LRU case?
>
> >         setup at destination = 7263.67
>
> Again, the setup time of 7.2ns is completely off-base and suggests an
> improper parsing of the FreePDK45 liberty file.  The liberty file syntax
> is not so much a spec as it is an amalgam of numerous competing formats.
> It is probably the worst file format invented since EDIF.
>
> I am a bit backed up on things but I'll look into it.  I need to see if
> there is a repeatable case.
>
> Clearly the difference between the 1.9ns throughput of the gates and the
> additional stated setup time of 7.2ns is the difference between running
> at 526MHz vs. running at 110MHz.  The setup time is the full difference
> between those two numbers.
>                                         Regards,
>                                         Tim
>
> +--------------------------------+-------------------------------------+
> | R. Timothy Edwards (Tim)       | email: tim at efabless.com             |
> | efabless, inc.                 | web:   http://www.efabless.com      |
> | 2570 N. 1st St., Suite 200     | phone: (240) 489-3255               |
> | San Jose, CA 95131             | cell:  (408) 828-8212               |
> +--------------------------------+-------------------------------------+
>


-- 
Øyvind Harboe, General Manager, Zylin AS, +47 917 86 146
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