( ESNUG 427 Item 9 ) -------------------------------------------- [04/14/04]
Subject: ( ESNUG 421 #2 ) One Customer's Impressions Of Nassda Lexsim
> A question to the ESNUG crowd: has anyone used Lexsim from Nassda?
> Likes? Dislikes? Any comments on accuracy, runtimes and capacity?
> I'd like to hear what the actual users have to say about it.
>
> - Yaron Kretchmer
> Altera Corp.
From: [ The Mouse That Roared ]
Hi John,
Anonymous, please. We use Lexsim to analyze the reliability of our power
network. It takes in a netlist from both the Synopsys and Mentor RC
extraction tools. Our power network is huge. Lexsim uses a special
algorithm to simplify it into a smaller network -- basically it is an
impedance-based network. Then it calculates how much current is drawn,
and brings the current information into the network and calculates IR drop.
The absolute numbers that Lexsim provides aren't so critical -- it is
really the relative number that matters. With these you can determine
(for example) whether you need to add more metal layers or more vias.
There are two things a Lexsim user needs to pay special attention to.?
1) The vector generation for the Lexsim. The vectors should cover the
worst case scenario of toggling the maximum number of nodes.
2) The user has to understand the reduction schemes of Lexsim (for your
power network) and HSIM (for the signal nets) to run the tools
efficiently. Performance-wise Lexsim seem to be as good as HSIM as
far as run time, capacity and accuracy so far.
My biggest criticism is with regards to Lexsim RA. With Lexsim alone,
the IR drop information is presented in a text file. If you want to export
the information into a viewer (like Cadence), you must also buy from
Nassda a copy of Lexsim RA.
Also Lexsim won't work if used incorrectly. You must understand your
design intimately to use Lexsim efficiently. You have to have the
correct options set for Lexsim to work properly.
I've been using Lexsim for past 6 months and its results have been good.
- [ The Mouse That Roared ]
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