摘要:
A timing graph representing timing information of an integrated circuit design may change after modifications are made to the integrated circuit design. The modifications change timing parameters for edges in the timing graph. The measure of these changes may be computed at a computed measure compared to a threshold. In the event the measure exceeds the threshold, the edges in the timing graph that need to change in response to the modifications are updated. Otherwise, the current edges in the timing graph are continued to be used. The threshold is set in accordance with the accuracy and efficiency requirements of an electronic design automation tool.
摘要:
A method for design optimization using logical and physical information is provided. In one embodiment, a method for design optimization using logical and physical information, includes receiving a behavioral description of an integrated circuit or a portion of an integrated circuit, optimizing placement of circuit elements in accordance with a first cost function, and optimizing logic of the circuit elements in accordance with a second cost function, in which the optimizing placement of the circuit elements and the optimizing logic of the circuit elements are performed concurrently. The method can further include optimizing routing in accordance with a third cost function, in which the optimizing routing, the optimizing placement of the circuit elements, and the optimizing logic of the circuit elements are performed concurrently.
摘要:
The present invention, generally speaking, provides a placement method for the physical design of integrated circuits in which natural topological feature clusters (topo-clusters) are discovered and exploited during the placement process. Topo-clusters may be formed based on various criteria including, for example, functional similarity, proximity (in terms of number of nets), and genus. Genus refers to a representation of a netlist in terms of a number of planar netlists—netlists in which no crossing of nets occurs. Topo-clusters drive initial placement, with all of the gates of a topo-cluster being placed initially in a single bin of the placement layout or within a group of positionally-related bins. The portion of a topo-cluster placed within a given bin is called a quanto-cluster. An iterative placement refinement process then follows, using a technique referred to herein as Geometrically-Bounded FM (GBFM), and in particular Dual GBFM. In GBFM, FM is applied on a local basis to windows encompassing some number of bins. From iteration to iteration, windows may shift position and vary in size. When a region bounded by a window meets a specified cost threshold in terms of a specified cost function, that region does not participate. The cost function takes account of actual physical metrics—delay, area, congestion, power, etc. “Dual” refers to the fact that each iteration has two phases. During a first phase, FM is performed within a region on a quanto-cluster basis. During a second phase, FM is performed within the region on a gate basis. GBFM occurs in the context of recursive quadrisection. Hence, after GBFM has been completed, a further quadrisection step is performed in which each bin is divided into four bins, with a quarter of the gates of the original bin being placed in the center of each of the resulting bins. GBFM then follows, and the cycle repeats until each bin contains a fairly small number of gates. Following the foregoing global placement process, the circuit is then ready for detailed placement in which cells are assigned to placement rows.
摘要:
A design tool for integrated circuits includes a placement tool which concurrently places logic gates and interconnect. In one embodiment, the logic gates are placed into bins and virtual buffers are inserted between logic gates mapped to different bins. Placement and interconnect wire lengths and densities are successively improved leading to removal of some buffers and actualization of the virtual buffers.
摘要:
This invention recognizes the ability of logic optimization to help placement relieve congestion. Different types of logic optimizations are used to help placement relieve congestion. In one type of optimization, the speed of parts of the circuit is improved by selecting faster cells. In another type of optimization, the topology of the circuit is changed such that placement can now move cells, which could not have been moved before, to reduce congestion and thus enable routing. A distinguishing feature of this methodology is that it not only uses the placement information for interconnection delay/area estimates during logic optimization, but also uses logic optimization to aid the physical placement steps by providing support to placement so that the congestion of the circuit is improved. The aim is to avoid getting into a situation where the placed circuit cannot be routed.
摘要:
The disclosure describes a placement method for the physical design of integrated circuits in which natural topological feature clusters are discovered and exploited during the placement process is disclosed. Topo-clusters drive initial placement, with all of the gates of a topo-cluster being placed initially in a single bin of the placement layout or within a group of positionally-related bins. An iterative placement refinement process is done using a technique referred to as Dual Geometrically-Bounded FM (GBFM). GBFM is applied on a local basis to windows encompassing a number of bins. From iteration to iteration, windows may shift position and vary in size. When a region bounded by a window meets a specified cost threshold in terms of a specified cost function, that region stops participating. Following the foregoing global placement process the circuit is then ready for detailed placement in which cells are assigned to placement rows.
摘要:
A design tool for integrated circuits includes a placement tool which places logic gates and interconnect components concurrently. Probabilistic interconnect models are used to represent the collection of possible interconnect routings that provide acceptable circuit performance and routing area.
摘要:
The large-scale process and environmental variations for today's nano-scale ICs are requiring statistical approaches for timing analysis and optimization (1). Significant research has been recently focused on developing new statistical timing analysis algorithms (2), but often without consideration for how one should interpret the statistical timing results for optimization. The invention provides a sensitivity-based metric (2) to assess the criticality of each path and/or arc in the statistical timing graph (4). The statistical sensitivities for both paths and arcs are defined. It is shown that path sensitivity is equivalent to the probability that a path is critical, and arc sensitivity is equivalent to the probability that an arc sits on the critical path. An efficient algorithm with incremental analysis capability (2) is described for fast sensitivity computation that has a linear runtime complexity in circuit size. The efficacy of the proposed sensitivity analysis is demonstrated on both standard benchmark circuits and large industry examples.
摘要:
Active resistors for reduction of transient power grid noise. An active resistance added in parallel to the operating circuit blocks of a semiconductor device. This resistance increases the damping ratio of the power grid, which in turn decreases the number and the magnitude of oscillations and/or noise resulting from step disturbances of the power supply current. The active resistance can implemented by a transistor connected to a bias voltage. Alternatively, the active resistance can be implemented by a drive transistor with a gain stage, or two active resistors where one responds to overshoots in the current flow and the second active resistor responds to droops in the current flow.
摘要:
The large-scale process and environmental variations for today's nano-scale ICs are requiring statistical approaches for timing analysis and optimization (1). Significant research has been recently focused on developing new statistical timing analysis algorithms (2), but often without consideration for how one should interpret the statistical timing results for optimization. The invention provides a sensitivity-based metric (2) to assess the criticality of each path and/or arc in the statistical timing graph (4). The statistical sensitivities for both paths and arcs are defined. It is shown that path sensitivity is equivalent to the probability that a path is critical, and arc sensitivity is equivalent to the probability that an arc sits on the critical path. An efficient algorithm with incremental analysis capability (2) is described for fast sensitivity computation that has a linear runtime complexity in circuit size. The efficacy of the proposed sensitivity analysis is demonstrated on both standard benchmark circuits and large industry examples.