( ESNUG 383 Item 9 ) -------------------------------------------- [11/28/01]
Subject: ( ESNUG 380 #11 ) Watch Out! That VCS PLI *Will* Drag You Down!
> Gregg Lahti's letter got me concerned that many VCS customers might not
> be running VCS as fast as they could. VCS does not have nearly as
> many switches as DC, but it is very important to understand the affect
> of switches on VCS' performance. Please post this reply to show your
> readers a quick overview about maximizing VCS performance.
>
> - Mark Warren
> Synopsys, Inc. Cupertino, CA
From: Anders Nordstrom <andersn@sympatico.ca>
Hi John,
In ESNUG 380 #11, Mark Warren from Synopsys wrote about what switches to
use to get faster RTL simulations in VCS. I spent weeks trying different
combinations of switches without getting much more than 10 to 20 percent
improvement. I wasn't even using the PLI and still there was something
slowing down my simulation.
It turned out that the PLI was the problem after all. Not because I used
it but because it was there. At Nortel, our cad support distributes VCS
with several PLI routines already linked in so that we can try different
waveform viewers and code coverage tools.
By running VCS with only the Signalscan PLI compiled in VCS (but not used),
I got a speed-up of 8 to 10 percent on a 3 Mgate RTL design and close to
20 percent on a 500 kgate RTL design.
By not compiling in any PLI routines I got a speed-up of 42 to 48 percent
on both my small and large design.
Of course, the VCS PLI is useful for waveform viewers and code coverage
tools, but I you should never even link in the VCS PLI routines if you
are not going to use them.
- Anders Nordstrom
Nortel Networks, Ltd. Ottawa Canada
|
|
