The KIM-1 and classic 6502 related topics. Zero page FTW!
KIM-1
Happy 49th Birthday, Apple II.
Rather an important 6502 system!
The MOS 6502 was such a GREAT CPU and used in many games systems and home computers starting in the mid 70s through the 80s and early 90s.
The 6510 in the C64 was a 6502 with I/O port pins for bank switching. Same instruction set. Slightly different pinout.
1977: The Apple II, one of the first personal computers, goes on sale. Designed primarily by Steve Wozniak its 6502 microprocessor runs at 1 MHz, programs are loaded from cassette tape and it comes with just 4kB of RAM – the price is $1,298.
Tinkered a bit in the 'visual cpu remix' tools so that the mouse wheel zoom is centered on the mouse pointer (also fixed a Dear ImGui debug assert that slipped through when updating to some recent Dear ImGui version)
z80: floooh.github.io/visualz80rem...
6502: floooh.github.io/visual6502re...
The 6502, or any of the 8 bit processors, is simple enough that one person can understand the entire system, from the memory all the way to the operating system. The same can not be said for any of the latest Wintel systems.
Quite a bit different pinout:
Now with pinout for the MOS 6510 (and related notes)!
masswerk.at/6502/6502_in...
The C64 used 3 bits for memory control (switching between ROM, RAM, and IO at the top of the memory map), and 3 bits for the cassette interface.
You probably don't want to be switching out IO for long though.
Some of you may be wondering, "Why is Joe doing this? There's already a hundred 6502 single board computers out there!"
And the answer is: to live through and learn from the process of designing one, like the "old ones" did in the before times.
Oh, and because it's fun. I thoroughly enjoy it.
