( ESNUG 373 Item 16 ) ------------------------------------------- [06/07/01]
Subject: ( ESNUG 372 #4 ) PhysOpt Rival Agrees Congestion Is Pain In Ass
> Though our design's overall row utilization is low, about 55%, PhysOpt
> (since it doesn't have real global routing) keeps clustering cells to
> create very high density areas. This happens with -congestion option,
> even when we leave empty space around the cluster. This congestion makes
> our design unroutable.
>
> - [ Shrek's Donkey ]
From: Keith Mueller <keith@siperspective.com>
Hi John,
We have seen a number of designs that exhibit the same congestion issue
using several of the physical synthesis tools, so this problem is not
unusual, particularly in switching blocks in networking chips. These
blocks tend to be very large (sometimes pushing 500K cells which of course
is too large for physical synthesis), with a large number of ports on all
sides of the block and wide busses running every direction. It is a very
tough placement problem to get a routable implementation on these low
density, highly interconnected blocks.
Silicon Perspective's First Encounter is able to control the placement
density on a module-by-module basis within the block, so we can selectively
relieve the congestion.
- Keith Mueller
Silicon Perspective Corp. Santa Clara, CA
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