The IBM SP95 SRAM is a new integrated circuit for mainframe memory. While bipolar memory offered improved performance over magnetic-core memory, it could not compete with the lower price of magnetic-core which was being mass produced.
The advent of the MOS transistor was able to switch at amazing speeds, The problem is that a flip-flop needs 6 transistors. MOS is smaller than bipolar but it was not available for mainframes,
Still the bipolar RAM was substantially more powerful in speed. Flip-flop designs failed to gain ground however so only a few models of System/360 were built with the RAM. The model 95 was the first machine equipped with the higher speed memory.