Z80 Single Board Computer

This is my first didactic 8bit – Z80 based computer.

I’ve made it because I was interested into homebrew such type of computer since high-scool times but never do it. I was intrigued by the idea of better understanding of PC architecture and  I wish to learn programming with assembler language.

My project starts copying Grant Searle’s magnificent project: Grant’s 7 chip Z80 Computer Please note that I’ve changed the way of the UART/RS232 converter is wired. In fact I’ve lost a lot of time following Grant’s schematic: everything double cecked but no data received to the serial port… uhm… I’ve solved in this way:

No jumpers between DB9 connector pins or other RTS shit… just a simple straight RX-TX converter between 6850 UART and DB9 connector.

I’ve build it using point-to-point wire soldering on a veroboard prototyping board. At the moment it comunicate with me via a RS232 serial link.

The schematic is the same of the Searle’s website except I’ve modified the clock source and the init.asm code that drive the 68B50 ACIA.

I’m using a 1.8432Mhz crystal oscillator at first for cpu and ACIA then switched to drive the cpu via a 10.240Mhz crystal oscillator. The 1.8432Mhz crystall just drive the ACIA.

I’ve benchmarked it’s performance via the Mandelbrot generator provided by the RC2014 project.

color_mandelbrot    mandelbrot

This RC2014 project started years ago like mine copying the Searle’s project and improving it so it’s 100% compatible with mine.

The results? At 1.832Mhz it took 46:52 Minutes to complete. At 10.240Mhz just 8:31 minutes



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