The analysis in this paper shows a multiprocessor like C.mmp to have a factor of three to four cost/performance advantage over uniprocessor systems such as the PDP-10 when implementations using similar technologies are considered. This comparison is shown to be very sensitive to memory prices and considerable attention is given to normalizing memory costs between C.mmp and the PDP-10. An important part of this analysis is a comparison of the PDP-10 architecture with the PDP-11 architecture (i.e. the architecture of the processors of C.mmp). When the limited address space of the PDP-11 is not a problem, we see that to a close approximation it takes the same number of PDP-11 instructions (average length 25 bits) as PDP-10 instructions (length 36 bits) to represent a program. While the comparison in this paper explicitly considers multiprocessor degradation factors such as memory interference, it does not address the problem of writing software systems capable of taking full advantage of the multiprocessor structures. The comparisons in this paper are primarily ofcused on comparing the hardware structures of uniprocessors and multiprocessors. Work is now in progress at CMU that is attempting to evaluate the effectiveness of both individual multiprocessor structures application programs and multiprogrammed systems operating on C.mmp.