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Show 67 operating concurrently. Thus, the above arguments apply to these subarrays too. Therefore, a bundled datapath approach using DCFL seems like a cost effective solution. Another reason for using DCFL was that there exists a library of cells implemented in DCFL in the ACME database that could be directly used in the design whereas in the case of the precharged logic family, all the cells would have to be laid out from scratch. Finally, the third reason for using DCFL was that it is a well tested and used logic family whereas our precharged logic circuits are still under development. 4.3 An Overview of ACME ACME is a VLSI CAD tool developed here at the University of Utah. In this section only a very brief overview of the system is presented. It has been described in detail elsewhere [16]. Its main features are: • It is an X-windows based system that allows designs to be captured hierarchically. • It combines both schematic capture and the physical design in one step. • It provides an interface to functional simulation tools such as SIMPPL [21], HILO, etc. as well as circuit simulators such as SPICE. • It provides CIF to be generated from the design directly thus providing an interface to the foundry. • Since it allows logic design and physical design to be combined in one step, the parasitic capacitances can be accurately calculated and accounted for in simulations • By the same token, since the physical placement is under manual control, better optimization of the stray capacitances and area can be done. |
