Simultaneous functional and timing ECO

Abstract

Metal-only ECO is prevalent at design houses to perform incremental design changes to resolve last found functional and/or timing failures. However, it is hard to perform mixed functional and timing changes manually. Prior endeavors focus on functional or timing ECO alone, but we observe that separating them may fail to fix all timing violations. Consequently, this paper presents the first work to perform simultaneous functional and timing ECO. We use an augmented bipartite graph to model both types of ECO. In addition, through comprehensive constant insertion and bridging, the functional capability of each spare cell is enhanced, thus facilitating spare cell selection. Experimental results show that our simultaneous functional and timing ECO engine can successfully resolve mixed functional and timing ECO that is unsolvable by the sequential scheme. Moreover, our engine outperforms the state-of-the-art works for timing ECO with a 117X speedup, and for functional ECO with 6-15% wirelength reductions.

Timing ECO optimization using metal-configurable gate-array spare cells

“…Constraint (9) ensures that each critical gate is assigned to exactly one position. Constraints (10) and (11) guarantee that each tile is occupied by at most one gate. Based on Theorem 1, tiles 1 to i∈G si should be occupied, and tiles i∈G si + 1 to |T | should not be occupied.…”

“…Metal-only ECO has been extensively studied in recent literature [2,3,4,5,6,7,8,9,10,11]. To enable metalonly ECO, these works use pre-inserted redundant standard cells as spare cells.…”

Functional ECO Using Metal-Configurable Gate-Array Spare Cells

“…These incremental changes can be functional ECO, dedicated for functional rectification or specification modification, or timing ECO, dedicated for timing closure and optimization. Recently, metal-only ECO has drawn great attentions in literature, e.g., [2,3,4,5,6,7,8,9,10,11,12,13]. To enable metal-only ECO, (redundant) spare cells are inserted at the early placement and routing stage.…”

“…To enable metal-only ECO, (redundant) spare cells are inserted at the early placement and routing stage. Most of prior works regard standard cells as spare cells, e.g., [2,3,4,5,6,7,8,9,10,11]. Nevertheless, these pre-inserted standard spare cells are limited by their pre-determined quantity, functionality, and locations.…”

Timing-constrained replacement using spare cells for design changes

“…However, prior works only consider the functional or timing ECO problem. Recently, the functional and timing ECO problems in a complex design are concurrently considered in [3] [4]. However, both of their works neglect the timing effect due to spare cell rewiring such that timing violation may be generated after performing functional ECO.…”