Microsystems, and IBM Distributed Services (DS). DS had the distinction of being built on top of SNA, and thereby being fully compatible with DS on the IBM midrange AS/400 and mainframe systems. For the graphical user interfaces, AIX v2 came with the X10R3 and later the X10R4 and X11 releases of the X Window System from MIT, together with the Athena widget set. Compilers for C and Fortran programming languages were available. Some RT PCs were also shipped with the Academic Operating System (AOS), an IBM port of 4.3BSD Unix to the RT PC. It was offered as an alternative to AIX, the usual RT PC operating system, to US universities eligible for an IBM educational discount. AOS added a few extra features to 4.3BSD, notably NFS, and an almost ANSI C-compliant C compiler. A later version of AOS existed that was derived from 4.3BSD-Reno, but it was not widely distributed. The RT forced an important stepping-stone in the development of the X Window System, when a group at Brown University ported X version 9 to the system. Problems with reading unaligned data on the RT forced an incompatible protocol change, leading to version 10 in late 1985. Sales and market reception The IBM RT had a varied life even from its initial announcement. Most industry watchers considered the RT as "not enough power, too high a price, and too late." Many thought that the RT was part of IBM's Personal Computer line of computers. This confusion started with its initial name, "IBM RT PC". Initially, it seemed that even IBM thought that it was a high-end Personal Computer given the initially stunning lack of support that it received from IBM. This could be explained by the sales commission structure the IBM gave the system: salesmen received commissions similar to those for the sale of a PC. With typically configured models priced at $20,000, it was a hard sell, and the lack of any reasonable commission lost the interest of IBM's sales force. Both MIT's Project Athena and Brown University's Institute for Research in Information and Scholarship found the RT inferior to other computers. The performance of the RT, in comparison with other contemporaneous Unix workstations, was not outstanding. In particular, the floating point performance was poor, and was scandalized mid-life with the discovery of a bug in the floating point square root routine. With the RT system's modest processing