Considerations in block-oriented systems design

The feasibility of transmitting blocks of words between memory and CPU is the subject of this study. The question is pertinent to the design of very fast computing systems where the nanoseconds to traverse a few feet become significant. There is intuitive advantage to transmitting blocks of words, rather than a word at a time. The initial access time due to physical distance, effective address mapping, and priority is a few hundred nanoseconds. If this time could be prorated against several words, then the effective access time could be reduced to a few tens of nanoseconds. The question is, of course, can the extra words be useful to the CPU? This question was explored in a simulation model driven by customer-based IBM 7000 series data. The simulation results indicate that blocks of 4, 8, or 16 words, transmitted to a local storage of 2K to 4K words, will adequately prorate memory access time. With this configuration, block transfer is seen to be an efficient memory access method which can provide high performance, superior to single-word access.