Now and again we have discussions about ways to improve the 6502 instruction set architecture - sometimes about backward-compatible changes and sometimes about new machines which bear some resemblance. Sometimes we even have a design which puts the ideas into a concrete form. I thought it might be useful to index, so I went searching. Treat this as a list in random order, subject to getting new entries!

(These are threads about architecture, as distinguished from threads about faster implementations like this one. You'll find some related discussions about homebrew CPU architectures over at anycpu, for example this one.)

- Who's interested in wide-byte 6502 variants like 65Org16?
- The RTF65002 Core
- Instructions that I missed
- Proposed instruction set for the 65m32
- Improving the 6502, some ideas (the thread which, among other ideas, introduces the 65Org32)
- Defining the 65Org32 - addressing modes (and instructions)
- M65C02A Core
- The RTF65002 Core
- "Improved" 6502
- The 65k project!
- Stack/PC-relative addressing: signed or unsigned? (65k)
- Disappointment with 32-bit 6502 attempts
- prefix bytes: an idea for 65Org816
- Make a standard 6502 32bit capable
- ARM: "inspired by" 6502?
- Instruction set Design - Reasoning?
- Looking for feedback on my CPU project
- Cache in FPGA
- "Homebuilt" 6502 cpu's
- The KimKlone: a radical 6502 redesign
- 6519 Forth processor
- MOS 6509 look-alikes?
- 65Org16 - extending the instruction set
- 6502 redundant, missed, and suggested features
- What if independent MOS Technology had survived?
- 65VM02
- How would YOU extend the 6502?

Related:
- Overview of 6502-like cores, hard, soft, partial, overblown
- 65x02 variants
- 6502ish projects and products listed by Garth
(updated 2017-05-01 and 2018-08-17 and 2020-08-11)