Editing MOS Technology (section)

===6502 family===
{{main|MOS Technology 6502}}
When the 6501 was announced, Motorola launched a lawsuit almost immediately. Although the 6501 [[instruction set]] was not compatible with the 6800, it could nevertheless be plugged into existing [[motherboard]] designs because it had the same functional pin arrangement and [[IC package]] footprint. That was enough to allow Motorola to sue. Allen-Bradley sold back its shares to the founders, sales of the 6501 basically stopped, and the lawsuit would drag on for many years before MOS was eventually forced to pay {{US$|200000}} in fines.

In the meantime MOS had started selling the [[MOS Technology 6502|6502]], a chip capable of operating at {{val|1|ul=MHz}} in September 1975 for a mere {{US$|25}}. It was nearly identical to the 6501, with only a few minor differences: an added on-chip clock oscillator, a different functional pinout arrangement, generation of the SYNC signal (supporting single-instruction stepping), and removal of data bus enablement control signals (DBE and BA, with the former directly connected to the phase 2 clock instead).<ref>{{Cite web|url=http://www.6502.org/documents/books/mcs6500_family_hardware_manual.pdf|title=MOS MCS6500 Microcomputer Family Hardware Manual (Publication Number 6500-10A), January 1976, p. 41.}}</ref>  It outperformed the more-complex 6800 and [[Intel 8080]], but cost much less and was easier to work with. Although it did not have the 6501's advantage of being able to be used in place of the Motorola 6800 in existing hardware, it was so inexpensive that it quickly became more popular than the 6800, making that a moot point.

[[Image:MOS Technologies large.jpg|thumb|Image of the circuit board of a [[Commodore 64]] showing some important MOS Technology circuits: the [[MOS Technology 6510|6510 CPU]] (long chip, lower left) and the [[MOS Technology SID|6581 SID]] (right). The production week/year (WWYY) of each chip is given below its name.]]

The 6502 was so cheap that many people believed it was a scam when MOS first showed it at a 1975 trade show. They were not aware of MOS's masking techniques and when they calculated the price per chip at the current industry yield rates, it did not add up. But any hesitation to buy it evaporated when both Motorola and Intel dropped the prices on their own designs from {{val|p=$|179}} to {{val|p=$|69}} at the same show in order to compete. Their moves legitimized the 6502, and by the show's end, the wooden barrel full of samples was empty.{{citation needed|date=October 2012}}

The 6502 would quickly go on to be one of the most popular chips of its day. A number of companies licensed the 650x line from MOS, including [[Rockwell International]], [[GTE]], [[Synertek]], and [[Western Design Center|Western Design Center (WDC)]].

A number of different versions of the basic CPU, known as the 6503 through 6507, were offered in 28-pin packages for lower cost. The various models removed signal or address pins. Far and away the most popular of these was the [[MOS Technology 6507|6507]], which was used in the [[Atari 2600]] and Atari disk drives. The 6504 was sometimes used in printers. MOS also released a series of similar CPUs using external clocks, which added a "1" to the name in the third digit, as the 6512 through 6515. These were useful in systems where the clock support was already being provided on the motherboard by some other source. The final addition was the "crossover" [[6510]], used in the [[Commodore 64]], with additional I/O ports.