IBM has changed the rules on its AIX/370 implementation of Unix, which runs under the VM operating system, and has switched from a flat monthly licence charge for the software to a graduated monthly charge tied to the size of 370 on which it is to run. The operating system now also supports the 3480 Magnetic Tape Subsystem. The thing goes on limited availability next quarter, and the AIX PS/2 programs that had been delayed to the fourth quarter will be available in the third – but only where they are to be used in conjunction with AIX/370. The supported version of VS Fortran under AIX/370 has also been put back one release users will now need VS Fortran 2.5 rather than 2.4. The graduated charges for AIX/370 range from a one-time $29,760 a month on a baby 9370 to $204,800 or $6,825 a month on a 3090 600S; for Network File System – AIX/370 NFS – prices range from a one-time $1,980 or $79 a month to $13,650 or $455 a month on a 3090-600S.