Asynchronous DRAM Design and Synthesis

Virantha Ekanayake and Rajit Manohar

We present the design of a high performance on-chip pipelined asynchronous DRAM suitable for use in a microprocessor cache. Although traditional DRAM structures suffer from long access latency and even longer cycle times, our design achieves a simulated core sub-nanosecond latency and a respectable cycle time of 4.8ns in a standard 0.25um logic process. We also show how the cycle time penalty can be overcome by using pipelined interleaved banks with quasi-delay insensitive asynchronous control circuits. We can thus approach the performance of SRAM, which is typically used for caches, while still benefitting from the smaller area footprint of DRAM.
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