( ESNUG 377 Item 6 ) -------------------------------------------- [09/19/01]
From: "Kirti Parmar" <kirti@magma-da.com>
Subject: ( ESNUG 374 #7 ) Magma R&D Responds To Customer's Technical Issues
Hello John,
My name is Kirti Parmar and I'm the Director of Product Engineering at
Magma. I would like to take a moment to respond to some items identified
by users in ESNUG 374 #7. I am very happy to recommend solutions to the
issues listed and look forward to your coverage of our customer issues.
Usability of the Power Router
-----------------------------
"Power router causing DRC and signal shorts."
"We found the Blast Fusion power router to be flaky. Had to fix
some of the power manually. Also the current version of the tool
does not allow to finish the power completely before the routing."
Point well taken. We have updated the Power Router in Release 3.0 which is
currently in beta. Our new GUI-driven power router is interactive and
supports complex power routing requirements. Because it is interactive and
immediately displays the results, any issues or problems that may be induced
are immediately visible. We believe this will address many of the issues.
On-line basic Power DRC checking capabilities (which can be disabled through
the GUI) are also available in Release 3.0.
Tie-Off Routing
---------------
"Tie hi/lo pins handled by power router instead of detail router."
"...but macro pin changes or tie hi/lo pin changes are difficult
to implement."
In Release 3.0, tie-offs for standard cells are handled during detail
routing. Tie-off for "macros" is still done during power routing because
these pins frequently require special rules.
We also provide an ability to define/redefine tie-off pins on a pin-by-pin
or on a per-net basis in Release 3.0. Tie-offs can be done directly to
power/ground nets or to special tie-off cells.
Antenna Avoidance and Repair
----------------------------
"We did have to do our own workarounds for antenna fixes, tho."
"Took some work before we got the tool to fix all antenna violations"
Antenna avoidance and repair have always been an integral part of the
Blast Fusion design flow. Magma models antenna effects from the first
global routing and takes these into account throughout the flow. However,
these have sometimes come at the expense of run time or increased
congestion (specially if incorrect antenna rules had been set) in some
designs. Repairing these often required tedious manual intervention.
Clearly the status quo was unacceptable as antenna rules become increasingly
stringent in newer (0.15u and smaller) process technologies.
Beginning with Blast Fusion version 2.1 we have added area-based antenna
rules to support these new technology requirements. Enhancements are
planned for Blast Fusion version 3.0 which will focus on avoiding and
resolving antenna problems in a more localized area through "jumpers" and
"diode insertion". Our internal experiments indicate that this solution
produces high quality, antenna-free routing without increasing congestion.
Off-Grid Pins Handling
----------------------
"Detail router doesn't always find a solution for off grid closely
spaced pins on macros."
Blast Fusion requires proper modeling and library preparation in order
to achieve optimal result in the presence of off-grid pins. We found
that the quality of results produced using Blast Fusion was unnecessarily
reliant on steps that could be automated in some cases. I am pleased to
say that we have taken steps to correct this. Release 3.0 of Blast Fusion
contains both algorithmic improvements as well as minor flow changes to
address this issue.
Built-In DRC and LVS Checking
-----------------------------
"All but 1 weren't using Magma's built in DRC/LVS capabilities. They
were mostly using Menter's Calibre + a few Avanti Hercules users."
"The ASIC vendors are responsible for the top level assembly and that
includes transistor level DRC/LVS. We always run the "basic" cell
level LVS/DRC built into Apollo and it seems most design rule errors
are found at that level."
"In Blast Fusion, we found a lot of bugs and many differences with
sign-off rules. Most of these are related to routing issues."
Blast Fusion has always had a rather extensive set of DRC and LVS checking
capabilities built-in. The capabilities include checking for shorts,
same-net and different net spacing violations, notches, antennas, islands,
via overhang, multi-port and other physical or connectivity violations based
on specified rules.
The richness of the available rule set notwithstanding, it is unfair to
characterize these capabilities as lacking when compared to other Place and
Route tools. Blast Fusion, like other similar tools, models geometries only
on the layers that there will be routing on. Other layers are "abstracted".
The recommended use model for Blast Fusion is to use the built-in DRC and
LVS capabilities to get the design "clean" from a place-and-route perspective
and, at the end, follow this DRC and LVS checking using external tools such
as Mentor's Calibre, Cadence's Dracula or Avanti's Hercules. We internally
use Calibre for QA testing.
We consider it an urgent bug if violations for the specified rules are not
reported by Blast Fusion but are reported by external DRC/LVS checking tools
like Calibre, Dracula or Hercules. Vice versa, we consider it a bug if a
violation is reported by Blast Fusion but is not reported by Calibre,
Dracula or Hercules given comparable rules.
As an aside, I would like to point out one feature of Blast Fusion that
users may not be aware of: the ability to import DRC violation markers from
report files produced by Calibre, Dracula or Hercules. The command is
"import marker calibre" (or "import marker dracula" or "import marker
hercules" as may be appropriate) which parses the specified report file
produced by Calibre, Dracula or Hercules and displays the violations in the
Blast Fusion GUI.
GUI
---
"GUI crashes more than it should, ..."
"The interactive GUI is still a little flakey."
I must concur with this assessment. We are improving the stability of the
GUI as well as increasing its functionality (the new interactive Power
Router is one of these). In Blast Fusion 3.0 we have made significant
improvements in the stability and performance of the GUI. The GUI is, and
will continue to be an area of focus for Magma as we strive to improve
Blast Fusion.
We appreciate the honest feedback we have received. Thanks.
- Kirti Parmar, Director of Product Engineering
Magma Design Automation, Inc.
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