computing arm of their UNIVAC division. Control Data Corporation Cray, along with William Norris, later became dissatisfied with ERA, then spun off as Sperry Rand. In 1957, they founded a new company, Control Data Corporation. By 1960 he had completed the design of the CDC 1604, an improved low-cost ERA 1103 that had impressive performance for its price. Even as the CDC 1604 was starting to ship to customers in 1960, Cray had already moved on to designing other computers. He first worked on the design of an upgraded version (the CDC 3000 series), but company management wanted these machines targeted toward "business and commercial" data processing for average customers. Cray did not enjoy working on such "mundane" machines, constrained to design for low-cost construction, so CDC could sell many of them. His desire was to "produce the largest [fastest] computer in the world". So after some basic design work on the CDC 3000 series, he turned that over to others and went on to work on the CDC 6600. Nonetheless, several special features of the 6600 first started to appear in the 3000 series. Although in terms of hardware the 6600 was not on the leading edge, Cray invested considerable effort into the design of the machine in an attempt to enable it to run as fast as possible. Unlike most high-end projects, Cray realized that there was considerably more to performance than simple processor speed, that I/O bandwidth had to be maximized as well in order to avoid "starving" the processor of data to crunch. He later noted, "Anyone can build a fast CPU. The trick is to build a fast system." The 6600 was the first commercial supercomputer, outperforming everything then available by a wide margin. While expensive, for those that needed the absolutely fastest computer available there was nothing else on the market that could compete. When other companies (namely IBM) attempted to create machines with similar performance, they stumbled (IBM 7030 Stretch). In the 6600 Cray had solved the critical design problem of "imprecise interrupts", which was largely responsible for IBM's failure. He did this by replacing I/O interrupts with a polled request issued by one of ten so-called peripheral processors, which were built-in mini-computers that did all transfers in and out of the 6600's central memory. The following CDC 7600 even improved the speed advantage by a factor of five. In 1963, in a