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.
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