The Cray-T90 was the last of the pure PVP single memory systems built by Cray Research. Around 20 of these systems were built from 1996 until 2000. The T90 reintroduced the idea of total immersion cooling last seen in the Cray-3 but retained the Model IOS used on the C90s. Under the covers a large tank(s) held the density packed boards using non-wire clip-on edge connectors. Available with 4 up to 32 processors and memories up to 8 GBytes. CPU versions that directly supported IEEE floating point maths were available. A scalar cache and paged memory were also used. T94 versions could use secondary to air heat exchangers.