Clock power minimization with regular physical placement of clock repeater components
View Patent ↗Power, routability and electromigration have become crucial issues in modern microprocessor designs. In high performance designs, clocks are the highest consumer of power. Arranging clocking components with regularity so as to minimize the capacitance on the clock nets can help reduce clock power, however, it may hurt performance due to some loss of flexibility in physically placing those components. The present invention provides techniques to optimally place clock components in a regular fashion so as to minimize clock power within a performance constraint. A rectangular grid is created and clock distribution structures are assigned to the grid intersection points. Latches are then located around the clock distribution structures to minimize an overall distance for connections between the latches and respective clock distribution structures. The horizontal and vertical pitches of the grid may be independently adjusted to achieve a more uniform spread of the clock distribution structures.
1. A method for designing the layout of a plurality of latches in two or more clock domains of an integrated circuit carried out by a computer system, comprising:
receiving an input layout of logic cells which include the latches located in a common plane, by executing first program instructions in the computer system;
creating a rectangular grid in a region of the integrated circuit containing the latches, the grid having grid intersection points defined by a horizontal pitch and a vertical pitch, by executing second program instructions in the computer system;
placing clock distribution structures at the grid intersection points in the common plane of the latches, said placing including bipartite matching of (i) cost and capacity for clock distribution structures to (ii) corresponding clock domains, by executing third program instructions in the computer system; and
locating the latches around the clock distribution structures to minimize an overall distance for connections between the latches and respective clock distribution structures, by executing fourth program instructions in the computer system.
2. The method of claim 1 wherein said locating includes bipartite matching of (i) cost and capacity for latches to (ii) corresponding clock distribution structures.
3. The method of claim 1 wherein at least one of the horizontal and vertical pitches is independently adjusted to achieve a more uniform spread of the clock distribution structures.
4. The method of claim 1 wherein the grid has a perimeter defined by a bounding box surrounding the latches.
5. The method of claim 1 wherein the grid has the same horizontal pitch and vertical pitch.
6. The method of claim 5 wherein the pitches are an integer less than or equal to h α according to the formula
h
α
=
-
(
W
+
L
)
=
(
W
+
L
)
2
+
4
WL
(
l
-
1
)
2
(
l
-
1
)
where W is the width of the grid, L is the length of the grid, and l is a predetermined number of clock distribution structures to be utilized.
7. A computer system comprising:
one or more processors which process program instructions;
a memory device connected to said one or more processors; and
program instructions residing in said memory device for designing the layout of a plurality of latches in two or more clock domains of an integrated circuit by receiving an input layout of logic cells which include the latches located in a common plane, creating a rectangular grid in a region of the integrated circuit containing the latches wherein the grid has grid intersection points defined by a horizontal pitch and a vertical pitch, placing clock distribution structures at the grid intersection points in the common plane of the latches, said placing including bipartite matching of (i) cost and capacity for clock distribution structures to (ii) corresponding clock domains, and locating the latches around the clock distribution structures to minimize an overall distance for connections between the latches and respective clock distribution structures.
8. The computer system of claim 7 wherein said locating includes bipartite matching of (i) cost and capacity for latches to (ii) corresponding clock distribution structures.
9. The computer system of claim 7 wherein at least one of the horizontal and vertical pitches is independently adjusted to achieve a more uniform spread of the clock distribution structures.
10. The computer system of claim 7 wherein the grid has a perimeter defined by a bounding box surrounding the latches.
11. The computer system of claim 7 wherein the grid has the same horizontal pitch and vertical pitch.
12. A computer program product comprising:
a computer-readable storage medium; and
program instructions residing in said storage medium for designing the layout of a plurality of latches in two or more clock domains of an integrated circuit by receiving an input layout of logic cells which include the latches located in a common plane, creating a rectangular grid in a region of the integrated circuit containing the latches wherein the grid has grid intersection points defined by a horizontal pitch and a vertical pitch, placing clock distribution structures at the grid intersection points in the common plane of the latches, said placing including bipartite matching of (i) cost and capacity for clock distribution structures to (ii) corresponding clock domains, and locating the latches around the clock distribution structures to minimize an overall distance for connections between the latches and respective clock distribution structures.
13. The computer program product of claim 12 wherein said locating includes bipartite matching of (i) cost and capacity for latches to (ii) corresponding clock distribution structures.
14. The computer program product of claim 12 wherein at least one of the horizontal and vertical pitches is independently adjusted to achieve a more uniform spread of the clock distribution structures.
15. The computer program product of claim 12 wherein the grid has a perimeter defined by a bounding box surrounding the latches.
16. The computer program product of claim 12 wherein the grid has the same horizontal pitch and vertical pitch.
17. The computer program product of claim 16 wherein the pitches are an integer less than or equal to h α according to the formula
h
α
=
-
(
W
+
L
)
=
(
W
+
L
)
2
+
4
WL
(
l
-
1
)
2
(
l
-
1
)
where W is the width of the grid, L is the length of the grid, and l is a predetermined number of clock distribution structures to be utilized.