The MOS Technology 8502 was an 8-bit

8-bit

The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...

 microprocessor

Microprocessor

A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...

 designed by MOS Technology

MOS Technology

MOS Technology, Inc., also known as CSG , was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor, and various designs for Commodore International's range of home computers.-History:MOS Technology, Inc...

 and used in the Commodore 128

Commodore 128

The Commodore 128 home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines...

. Based on the MOS 6510

MOS Technology 6510

thumb|300px|Image of the internals of a [[Commodore 64]] showing the 6510 CPU . The chip on the right is the [[MOS Technology SID|6581 SID]]...

 that was used in the Commodore 64

Commodore 64

The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...

, the 8502 added the ability to run at a double (2.048 MHz) clock rate, in addition to the standard 1.024 MHz rate used by the Commodore 64.

Since the 40-column VIC-II

MOS Technology VIC-II

The VIC-II , specifically known as the MOS Technology 6567/8562/8564 , 6569/8565/8566 , is the microchip tasked with generating Y/C/composite video graphics and DRAM refresh signals in the Commodore 64 and C128 home computers.Succeeding MOS's original VIC , the VIC-II was one of the two chips...

 display chip

Graphics processing unit

A graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...

 could not "steal" sufficient cycles when the CPU ran at double speed, video display in fast mode was available only with the 80-column VDC (unlike the VIC, which shares memory with the CPU, the VDC has its own dedicated video RAM in the C128). Some 40-column applications selectively disabled the screen when performing CPU-intensive calculations so that the additional speed could be utilized when the loss of video output was unimportant. A smaller speed gain, about 35%, was also possible while keeping the 40-column display active, by switching to 2MHz only while the VIC-II is drawing the vertical screen border, since no RAM access by the VIC is needed during that time.

The pinout is a little bit different from the 6510. The 8502 has an extra I/O-pin (the built-in I/O port mapped to addresses 0 and 1 is extended from 6 to 7 bits) and lacks the ϕ2-pin that the 6510 had.

In 2007, HP released the HP 35s

HP 35s

The HP 35s Scientific Calculator is, as of 2007, the latest in Hewlett-Packard's long line of non-graphing scientific and programmable calculators...

, a calculator that uses the Sunplus Technology 8502 microprocessor. This processor is not related to the MOS8502.