Friday, 5 November 2010

Visual 6502

Sometimes I stumble across something on the Internet that is just so utterly cool that I have to run around the room cackling manically. Yes, really.

Yesterday, thanks to Bunnie's Blog, I came across the Visual 6502 simulator.

The MOS 6502 computer chip was used in both the Apple Mac II and the initial Acorn BBC range of computers. As such, I cut my programming teeth on it; firstly with BBC Basic, and later 6502 Assembler.

These were in the days when a jump from 32Kb to 128Kb of memory opened new worlds (nowadays it is common to create temporary buffers of more than that); and 2MHz felt like undreamed-of speed. The 6502 was first made in 1975, and was far simpler (and cheaper) than the competing products from Intel and Motorola. As such, it was accessible to hobbyists, and was used in many early computers and computer kits.

The simulator simulates the operation of a 6502 chip using Javascript. It creates an image of the chip, allowing you to see how the signals are traced. It is a fantastically interesting piece of work, and an indication of how much computer technology has improved over the years. It should be noted that the simulator only works in very modern browsers that are HTML-5 compatible - you will also needs lots of memory and a fast computer. If your computer is not suitable, then goggle in amazement at the beautiful picture.

The writers have taken photographs of a 6502 chip, and designed the blocks from scratch; (i.e. reverse-engineered it). The simulator is complete enough to play games (albeit at a slow speed).

It is an amazing piece of work.

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