Quite a big system, a SBC or a bus based system. Lots of small cards like the RC2014, same busconnector.
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.
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.