May 14, 2017 · Third, MOS also created system support chips that were designed to easily interface with the 6502, such as the 6522 VIA. This made adding I/O capabilities very simple for system designers, and that freed them to focus more on custom circuitry that would help distinguish their system in the marketplace of many computers built around this basic ...

Jun 8, 2020 · There are, however, minor functional differences between the 6502 and the 65C02. If your application relies on undocumented opcodes, or makes creative use of certain bugs in the 6502, the 65C02 may not work for you. On the hardware side, three pins have been re-assigned in the WDC 65C02, compared to the 6502 and earlier (Rockwell) 65C02s.

May 21, 2022 · This is actually more true on the 6502 (so long as you tri-state its address lines during ϕ1). Essentially, the 6502 needs "double-speed" RAM because it does all RAM access during only half the cycle (ϕ2) and leaves it unused the on the other half (ϕ1). ϕ1 was often used for cheap, interference-free video framebuffers and RAM refresh.

Oct 17, 2020 · Reading the Wikipedia article about real-time computing, I found written that:. Once when the MOS Technology 6502 (used in the Commodore 64 and Apple II), and later when the Motorola 68000 (used in the Macintosh, Atari ST, and Commodore Amiga) were popular, anybody could use their home computer as a real-time system.

Apr 24, 2017 · The MOS 6502 (1 MHz) was introduced in 1975 for a price of $25. Then in 1978 MOS agreed to sell the 6502 (1.79 MHz) and an IO chip to Atari for $12 per set (because the production cost was $4). In 1977, the Zilog Z80A (4 MHz) was $65 for the ceramic package and $59 for the plastic version.

Apr 20, 2024 · The 6502 is a modified 6501. The 6501 was bus-compatible with the 6800, and could be used as a drop-in replacement in the same circuits electrically. It was this property that led to the legal issues that resulted in the 6502. The 6502 is perhaps inspired by, or in the same vein, as the 6800 but there is no direct relation.

Feb 9, 2019 · The main reason for removing the functionality was probably to avoid any licensing or royalty issues related to U.S. Patent 3991307 held by MOS at the time. The Ricoh 2A03/2A07 ASIC, together with the Ricoh Picture Processing Unit chip, comprise most of the necessary electronics for the NES by covering CPU, graphics display, controller inputs ...

Sep 25, 2024 · @RussellMcMahon: IMHO, the 6502 could have been made much more suitable for many I/O tasks if it had been designed so that all opcodes where the bottom two bits were 11 would behave as "branch if a 'branch enable' input is asserted at the midpoint of the next cycle, or alternatively if the function could be chosen by two wires among (1) single-byte NOP, (2) two …

Feb 7, 2021 · Assuming you’re asking: what can the 6502 be seen to be doing by an external observer, then the data sheet has a full breakdown of bus activity per cycle per addressing mode; that was long ago transcribed into ASCII form by the Commodore community and is now often sourced from that 64doc.txt.

Mar 10, 2020 · The 6502 in your photo actually has both, but some chips only had the oblong hole near pin 1. The differently sized holes made it easy to use a photo sensor to verify the correct orientation before bonding the die or placing the chip on a PCB (a photo sensor is simpler and more reliable than a mechanical sensor).