The Sysplex was to be based on CMOS (Complementary Metal Oxide Silicon) rather than the existing ECL (Emitter Coupled Logic) hardware. The cost of scaling the mainframe-unique ECL was much higher than CMOS which was being developed by a "keiretsu" with high-volume use cases such as Sony PlayStation to reduce the unit cost of each generation's CPUs. The ECL was also expensive for users to run because the gate drain current produced so much heat that the CPU had to packaged into a special module called a Thermal Conduction Module (TCM) that had inert gas pistons and needed plumbed to be high-volume chilled water to be cooled. But the air-cooled CMOS technology's CPU speed initially was much slower than the ECL (notably the boxes available from the mainframe-clone makers Amdahl and Hitachi). This was especially concerning to IBM in the CICS context as almost all the largest mainframe customers were running CICS and for many of them it was the primary mainframe workload.