The Cray-YMP Model E range was the direct successor to the YMP Model D and were manufactured from 1990 until 1994. Around 200 YMP machines were manufactured, and many customers migrated their workload from the Cray-XMP to a Cray-YMPs. These YMP systems used a Model-E Input-Output subsystem replacing the distinctive wings seen on the YMP Model D and were available with larger memory configurations and a choice of air or liquid secondary cooling. The YMP-2E was the first Cray supercomputer with a liquid to air heat exchanger built in. The YMP M90 was a large memory version of this technology.