PEYE can use the EYES system to estimate
the impact of modifications on the chip layout. This make it
possible to examine a range of possible modifications and
modification strategies with significantly less resources and in a
shorter time than can be achieved if the modifications where
applied to the whole layout. Using the sampled results it is
possible to identify which modifications should be applied to a
particular chip design.
Targeted Modifications
A further use of the sampling results is to define regions of a
chip where the a particular modification should be applied. Stated
another way, the sampling data can identify regions where a
modification need not be applied as there is little prospect of any
modifications of that type being applied to that region.
The ability to automatically exclude regions is particularly
useful where some large block of a design (e.g., RAM) is not
suitable for the modification. It is also useful where a
modification is split into sub types. For example, wire spreading
is implemented as displacement of horizontal wire and displacement
of vertical wire. Normally a metal layer runs in a preferred
direction but occasionally a block or chip region might have been
rotated and so the metal runs orthogonal to the preferred
direction. Rather than run both the horizontal and vertical wire
spreading routines over the whole design, sampled data can be used
to indicated where horizontal and vertical wires (that can be
modified) are likely to be.
The figure below shows such an example. Here metal3 normally
runs in the horizontal direction but some regions of the chip
contain vertical metal3, that sampling has shown can be modified.
In order to minimise the work required, "masks" of the regions
where modifications are to be implemented can be automatically
generated and used to direct the modifications applied to each
region.
