( ESNUG 478 Item 2 ) -------------------------------------------- [12/18/08]
From: Jason Ware <jware=user domain=cadence not calm>
Subject: Cadence has tweaked RTL Compiler Physical for better P&R results
Hi, John,
Could you please tell your readers about a change in our new 8.1 release
of Cadence RTL Compiler Physical?
RC-Physical has two major components to it:
PLE (Physical Layout Estimate) which is a model to better represent
physical capacitance during optimization;
and
Synth -to_placed which runs a full placement, trial route and
optimization.
This change affects PLE ONLY, there is no change to Synth -to_placed.
Since PLE is used by most of our ~400 RC customers now, I wanted to get
the word out through you.
PLE 8.1 has been reworked to be more accurate. Through experimentation
and customer feedback we found previous versions of PLE to be slightly
optimistic, which make physical timing closure more difficult. So the
algorithm was improved in 8.1. However it may make post-synthesis timing,
power, or area results look worse than previous versions.
Our experiments with this new model shows that the results are better in
P&R, which is what counts. So we HIGHLY recommend measuring QOR pre-CTS
optimization in P&R to make comparisons and would be interested in
feedback from users.
Starting 8.1.100 we have introduced a ple_mode called "global" which
is ON by default:
rc:\> get_attr ple_mode global
The 7.2 ple_mode was called "enhanced_physical".
Some of the features of the new model:
1) No dependence on enclosed area.
2) Ungrouping has no effect on timing with "global" ple_mode.
This is in agreement with how back-end tools behave.
3) Better correlation with back-end capacitances.
4) Still maintains the dynamic ability which has been the basis of PLE.
5) Works better with RC Physical.
John, please make your users aware of this change before they try using
RC Physical v8.1
Thanks!
- Jason Ware
Cadence Design Systems Plano, TX
Index
Next->Item
|
|
