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AR# 3657

MAP, PAR: Does Map or PAR insert global buffers on high fanout nets and/or unbuffered clock nets?

Description

Keywords: insert, global buffer, map, par, fanout, clock,
virtex, 4000ex

Urgency: standard

General Description:
MAP, PAR: Does Map or PAR insert global buffers on high fanout
nets and/or unbuffered clock nets?

Solution

4000E/L:
--------
No global buffer insertion

4000EX:
-------
The router for 4000EX/XL/XV will use any available global
buffer sites as routethrus for clock nets which are not
already buffered. If additional global buffers are left
over after all clock nets are allocated, they may also be
inserted on high fanout nets.

The key element in the scoring is how many K pin loads
are on the net. Because the placer and router share a
common scoring object for this, the placer can locate the
net's driver close to the selected global buffer site to
minimize overall routing delays.

Virtex:
-------
Virtex software will add global buffers to clock nets
AR# 3657
Date Created 03/20/1998
Last Updated 04/25/2000
Status Archive
Type General Article