took the process one step further and implemented an entire system on a single IC. Through the relentless effects of Moore's law, it was not long before the 3850 and 3851 could also be implemented in a single IC, which was released as the 3859. The line was also updated with the addition of the 3856, a 3851 with of ROM, and the 3857, a 3856 with additional address lines to access external ROM in addition to the 2 KB internal, eliminating the need for a separate 3853 in many roles. 3870 Around the same time that the 3859 was released, Mostek introduced their own version of a single-chip F8, the Mostek 3870. Whereas the 3859 was essentially just a single-chip 3850/3851, the 3870 was a significant advance; it ran up to , double that of the 3859, and required only a single power supply instead of +5 and +12. A much more important change was that custom ROM code was now masked onto the IC as the very last step in the process, so all of the CPUs were identical until the end of the production line. As a result, the mask fees were on the order of , which made it far less expensive to implement. The 3870 was such an advance over the original that Fairchild stopped production of the 3859 and licensed the 3870 for their own sales. The 3870 was modified with many sub-versions over time. Among the most important of these was the addition of a socket on top of the chip that allowed an EPROM to be plugged in with no other support circuitry required. This eliminated the need for the on-board ROM and allowed customers to produce their own ROM and eliminate the masking fees. Variations also included examples with more ROM or RAM or other more minor changes. Meanwhile, the cross-license deal with Olympia led to production in Germany by Telefunken, another of AEG's many brands. Mostek merged with United Technologies in 1979, who drove the company into the ground and in turn sold it to Thomson Semiconducteurs in 1985. Thomson merged with SGS in 1987 to form the modern STMicroelectronics, who continued to produce the 3870 into the 1990s. Fairchild also continued producing versions of the 3870 into the 1980s, when they were purchased by National Semiconductor. Although little-known today, "in 1977 the F8 was the world's leading microprocessor in