( ESNUG 424 Item 6 ) -------------------------------------------- [03/09/04]
Subject: ( ESNUG 421 #10 ) Magma BlastRail, EM, STA, and IR-drop Delays
> BlastRail:
>
> CONS
>
> I think Magma needs to add more functionality to optimize the power grid
> with minimal guard band. Their power analysis will not only have to take
> into account EM effect, but it will also have to be better integrated
> with the delay calculator and static timing analysis engine in order to
> take into account IR drop. It needs to ensure that any IR drop present
> will not impact circuit reliability or functionality.
>
> - Mike Newman
> Airgo Networks Palo Alto, CA
From: Pravin Sreeprakash <pravins=user domain=magma-da spot calm>
Hi John,
Magma's BlastRail not only takes into account EM issues but is also
completely integrated with the delay calculation and STA engine within
our Magma flow. BlastRail does have the capability to do instance-specific
derating based on the calculated voltage drops and do a static timing
analysis which accounts for these IR drops in the design. This capability
is a well integrated part of the Magma flow, thanks to Magma's unique
concept of a unified data model.
In order to turn on the IR-drop induced delay calculation feature, use the
following set of commands:
config cell voltage on
or
config cell voltage iterate
This command turns on the IR-drop induced delay feature. If set to
"iterate", the following set of steps can be run multiple times to finally
converge at a constant delay after a few iterations. If set to "on", one
round of iteration can be done to find out the effect of IR drop on delays.
Initial power consumption analysis is too pessimistic due to assumed ideal
voltages at all cell pins. This results in pessimistic voltage drop
numbers. In the next iteration, the power consumption analysis is usually
too optimistic due to lower supply voltage (and hence lower CV^2 etc.).
However, the slews are also slower which in turn increases the estimated
power consumption. Hence the need for multiple iterations.
Timing Analysis -> Power analysis -> IR drop analysis ===
/\ ||
|| \/
======Derated voltages used for next STA==========
The Tcl commands for the iterative analysis are as follows:
config cell voltage iterate
for { set i 0;} { $i < 3 } { incr i;} {
report timing path $m
report power analysis $m
report rail analysis vdrop $m
}
report timing path $m
The delays are found to increase during the first few iterations and
then tend to become stable after 3-4 iterations. Within the integrated
Magma flow, these iterations become less painful since they do not
involve any explicit file transfers and data translations between point
tool solutions for power analysis, voltage drop analysis and timing
analysis. The bottom line is that unlike point-tool flows, BlastRail
offers a more efficient solution that accounts for IR-drop induced delays.
- Pravin Sreeprakash
Magma Design Automation Bangalore, India
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