RAPPID Synchronization

Satyajit Chakrabarti and Sukanta Pramanik
Publishing date
September 08, 2003
8 pages
This paper proposes a solution to the synchronization issue in RAPPID that has prevented it from being used in synchronous processors like the Pentium family of processors, in spite of its higher average case throughput. Our first approach explores the possibility of using an early count of the number of instructions pending in the decoder. If the availability of these instructions can be predicted within a bounded time then the execution unit can carry on upto that point without error. Our second approach moves the possibility of metastability from the data path to the control path. The data is placed in the path before the control signal which ensures a stable data when the control is stable or metastable. If the metastability in control signal is not resolved within a single clock-cycle it is re-sampled and the re-sampled signal overwrites the previous signal, thereby ensuring a worst case latency of one clock-cycle.