The Josephson Technology as now understood is projected onto a current computer mainframe, the IBM 3033 to estimate its effect. This is a hypothetical projection and should not be taken in any way to represent a planned product. A three cycle critical case path is identified. Then an experimental 2.5-µm Josephson current injection logic (CII) circuit family and cache memory design are configured into a functionally equivalent Josephson package. Propagation distances in the hypothetical package are estimated to be 6 percent of those in the comparison mainframe; estimated cycle time is 4 ns yielding an internal performance improvement by a factor of = 14. The Josephson version of the IBM 3033 would entail a more than 99-percent reduction in regulated power. Copyright © 1981 by The Institute of Electrical and Electronics Engineers, Inc.