RC6502
Quite a big system, a SBC or a bus based system. Lots of small cards like the RC2014, same busconnector.
SBC schematic
Mini master
The Mini master project is a minified replica of the Apple 1
It’s built around a 6502 CPU, 6821 PIA (Peripheral Interface Adapter), RAM and ROM – just like the original Apple 1, but it uses an Arduino Nano to enable serial communication between the Apple 1 board and an external computer that acts as terminal.
That means you can’t hook up a keyboard and monitor directly to the board.
What has been done:
– Designed a PCB that can be easily produced and included in a **modular DIY kit** for anyone that wants to build this at home.
– Programmed the ROM so it only contains BASIC, Krusader (assembler) and the Woz Monitor (memory monitor).
– Written firmware for the Arduino to enable serial communication in a way that gives the real *Apple 1 feeling*.
– Written a simple utility to upload data to the computer. This proved to be difficult with existing tools as there need to be specific delays in sending the data.
Mini master Github Archive here
Mega6502
A replica of the Apple I using a 6502 and an ATMega.
The ATMega in this project takes care of everything – the 4k of RAM, the few bytes of ROM, the IO, and even the clock. With the 6502 you can have a little bit of fun with the clock; because the 6502 reads data off the bus a few nanoseconds off the falling edge of the clock and writes on the rising edge, [Dave] played around with the duty cycle of the clock to give the ATMega a bit more time to do its thing. With a 50% duty cycle, the 16Mhz ‘Mega has about eight cycles to decode an address and read or write some data. By making the low part of a clock cycle longer, he has about 45 cycles on the ‘Mega to do all the work. All of this was inspired by a fantastic tutorial on the 6502 clock.
Right now it has some hex values displaying on a small LCD, while the real I/O is handled by a serial connection to a computer. It’s retro enough, and a future update will include a faux cassette interface, possibly using an SD card for storage.
Links:
– WEIRD CLOCKS AND A TWO CHIP APPLE I
– Make your own Apple 1 replica. Dave Cheney
– Github archive
