At the time Unix was making major inroads into the supercomputing fields, but ETA decided to write their own EOS operating system, which wasn't ready when the first machines were delivered in late 1986 and early 1987. An operating system based on UNIX System V became available in 1988, as a result of porting work done under contract by the Canadian firm HCR Corporation, at which point it looked like the machine might finally succeed. Many sites that had refused to pay for their machines due to the low quality of EOS found ETA's UNIX completely usable and were willing to accept delivery.