- Easy 6502 (skilldrick.github.io)
In this tiny ebook I’m going to show you how to get started writing 6502 assembly language. The 6502 processor was massive in the seventies and eighties, powering famous computers like the BBC Micro, Atari 2600, Commodore 64, Apple II, and the Nintendo Entertainment System. Bender in Futurama has a 6502 processor for a brain. Even the Terminator was programmed in 6502.
- Build a 6502 computer (eater.net)
Learn how computers work by building and programming a computer with the classic 6502 microprocessor. This was the first truly low-cost microprocessor that started the personal-computing revolution. Versions of 6502 found their way into the Atari 2600, Apple II, Nintendo Entertainment System, Commodore 64, Atari Lynx, BBC Micro and many other computers and game consoles of the era.
compatibility with the 6510
- How MOS 6502 Illegal Opcodes really work (pagetable.com)
The original NMOS version of the MOS 6502, used in computers like the Commodore 64, the Apple II and the Nintendo Entertainment System (NES), is well-known for its illegal opcodes: Out of 256 possible opcodes, 151 are defined by the architecture, but many of the remaining 105 undefined opcodes do useful things.
- Reverse engineering ARM1 instruction sequencing, compared with the Z-80 and 6502 (righto.com)
When a computer executes a machine language instruction, it breaks down the instruction into smaller steps that are performed in sequence. For instance, a load instruction might first compute a memory address, then fetch a value from that address, and then store that value in a register. This article describes how the ARM1 processor implements instruction sequencing, performing the right steps in order. I also look briefly at the 6502 and Z-80 microprocessors and the different sequencing techniques they use.
- Nicole gets a real computer! The Microsoft Z80 SoftCard! (nicole.express)
So there I was, very happy with my Apple ][plus. But then I saw someone on the internet post, and it seems that my Apple is an overpriced box with a toy microcontroller for a CPU, while real computers use an Intel 8080, 8085 or Zilog Z80 to run something called “CP/M”… but I’ve already spent so much money on the Apple, so can I turn it into a real computer?
- The 6502 overflow flag explained mathematically (righto.com)
The overflow flag on the 6502 processor is a source of myth and confusion. In this article, I explain signed and unsigned binary arithmetic, discuss the meaning of the overflow flag, show various formulas for computing overflow, and dispell some myths about the overflow flag.
- The 6502 CPU’s overflow flag explained at the silicon level (righto.com)
In this article, I show how overflow is computed in the 6502 microprocessor at the transistor and silicon level. I’ve discussed the mathematics of the 6502 overflow flag earlier and thought it would be interesting to look at the actual chip-level implementation. Even though the overflow flag is a slightly obscure feature, its circuit is simple enough that it can be explained at the silicon level.
- 6502 Machine Language Tables and Aids (techtinkering.com)
When programming using machine code there are a few useful aids that can make it easier to do. I have created a couple of tables for the 6502 that can make the process easier. They are based on tables found in ‘Machine Code for Beginners’, which Usborne have made available as a PDF for free.
- Position Independent Code (6502) on the Commodore VIC-20 (techtinkering.com)
If we are writing 6502 machine code and want to to create a routine or program that can be placed in any location then we have to create Position Independent Code (PIC) or make the code relocatable. Here I’m going to show how to make our code Position Independent. There are three full examples near the end of the article which show how to put this altogether.
- MOS Technology 6502 (Wikipedia)
The MOS Technology 6502 (typically pronounced “sixty-five-oh-two” or “six-five-oh-two”) is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. The design team had formerly worked at Motorola on the Motorola 6800 project; the 6502 is essentially a simplified, less expensive and faster version of that design.