1. A method of physical circuit design comprising the steps of: packing components of a circuit design that are dependent upon an architecture of the circuit design; performing initial non-timing driven placement of the components of the circuit design; clustering, using a computer, two or more components of the circuit design into a cluster according to design constraints that limit at least one of inputs or outputs for the cluster to a threshold number that is less than a number of physical inputs or outputs, respectively, of a circuit structure in which the cluster is to be implemented, wherein the design constraints result in the circuit structure having a region that is unused by components of the cluster; wherein the threshold is one of the constraints, and the clustering includes: determining a number of required inputs and number of required outputs of the circuit structure required by the two or more components; in response to one of the number of required inputs or the number of required outputs being less than or equal to the threshold number, including the two or more components in the cluster; and in response to one of the number of required inputs or the number of required outputs being greater than the threshold number, not including the two or more components in the cluster; placing the components of the circuit design using timing driven placement after the clustering; declustering the circuit design; and performing post-placement placer tasks on the declustered circuit design.