AR# 11323


3.1i Virtex MAP- MAP may pack unrelated logic such that F5->F6 logic cannot be placed.


Keywords: F5MUX, F5/F6MUX , carry, macro, unrelated

Urgency: Standard

General Description:
Cases have been seen where MAP combines F5/F6MUX logic with carry logic during
unrelated packing. This occurs when none of the logic is RLOC'd. Because the placer
later constructs a carry macro out of the affected slices, the F5/FMUX slice pair is not
placeable because one slice is in the placer macro and one is not. The placer can only
handle the cases where both slices are in a macro or both are not.

As a result, PAR fails with the message:

ERROR:Place - Components abc and xyz are using the F5/F6MUX resources. The
component xyz is part of a carry chain macro. Please RLOC the components abc
and xyz together.


To work around this, either avoid unrelated packing or RLOC the F5/F6MUX logic.
Unrelated packing occurs when it is needed to fit the device to 100%, or when the
pack factor has be set lower (i.e., "-c 50"). Check the MAP report utilization summary
to determine how much unrelated packing, if any, occurred.

This problem will be fixed in the next major release after 3.1i, which is currently
scheduled for release in August, 2001. Unrelated packing will no longer combine carry
logic with F5/F6MUX logic.
AR# 11323
Date 08/19/2002
Status Archive
Type General Article
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