ACOS-6 (based on GCOS 8) is an obsolete high-end mainframe platform, which ceased active development in the early 2000s.
The first two models in NEC's SX series of supercomputers, the SX-1 and the SX-2 (released in 1985), ran an operating system derived from ACOS-4, which was variously called either SX-OS or SXCP (SX System Control Program).
[1][2][3] However, subsequent SX supercomputers, starting with the SX-3 (released in 1990), instead ran a derivative of Unix.
In late September 2012, NEC announced a return from IA-64 to the previous NOAH line of proprietary mainframe processors for ACOS-4, now produced in a quad-core variant on 40 nm, called NOAH-6.
In June 2022, i-PX AKATSUKI server equipped with NEC's original processor (NOAH-7) was released.