The modern ancestor of the desktop PC as we know it today was the IBM 5150 and arrived in 1981. It remained in production until 1987. The system, which is also famous for introducing PC-DOS, was a re-branded version of Microsoft's MS-DOS. The 5150 ran on an Intel 8088 4.77 MHz CPU and was praised for its high-quality construction and expandability. Of course, that was also due to the fact that the basic model did not include disk drives and just 16 kB of RAM. At its debut, the 5150 was priced at $1,565, which, however, quickly increased to more than $2,000 with two optional 160 kB 5.25-inch disk drives as well as optional 5, 10, or 20 MB hard disk drives.