65xx

65xx refers to a family of 8-bit microprocessors and microcontrollers derived from the MOS Technology 6502 architecture, later produced by Western Design Center (WDC). Introduced in the mid-1970s, the 6502 became a low-cost CPU that powered a wide range of early home computers, game consoles, and embedded systems, including the Apple II, Commodore PET, Atari 8-bit family, and the Atari 2600.

The core characteristics of the 65xx family include a simple, accumulator-based design with registers A, X, and Y, a stack pointer, a program counter, and a status register. The processors use an 8-bit data path but provide a 16-bit address bus, enabling a 64 KB address space. Their instruction set and addressing modes were designed for compact code and ease of use, supporting interrupts and a BRK instruction for software interrupt handling. The family is known for its influence on early personal computing and video game history.

Notable members and derivatives include various 6502-based CPUs and related peripheral components. The 6510 integrated I/O and timers used in the Commodore 64, while the 6504 and 6509 variants explored different memory configurations. Peripheral chips such as the 6520 PIA and 6522 VIA complemented the 65xx CPUs in many systems. The 65C02, produced by WDC, offered bug fixes and new instructions, and the 65CE02 introduced further enhancements. The 65816 is a significant 65xx extension that operates in 8- or 16-bit mode with bank switching, expanding to a larger address space and being utilized in platforms like the SNES and Apple IIGS.

Today, the 65xx lineage remains a key reference in retrocomputing and embedded applications, with ongoing production of select derivatives by WDC and continued historical interest in its architecture and impact.