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Brief Update...

A project log for Blinkenrechner

Computer based on a homemade 8-bit CPU

grant-giesbrechtGrant Giesbrecht 01/19/2021 at 03:510 Comments

I built my 2nd revision CPU (dubbed Zeta-2 because obviously it needs a badass name) and tested it's basic functionality. Manually operating the control lines, I was able to run each subsystem of the CPU and add, subtract, etc numbers. However, a number of issues cropped up regarding the control unit (ie. instruction decoder) and timing of read vs. write operations. I'll go into more detail about what went right/wrong in a later log. Anyway, I did redesigned the whole computer and added some really exciting features such as timer interrupts, quadruple the RAM, better controls + indicators, a 16 bit memory bus, and tons more. The design is complete and it's now a matter of putting the PCBs together in KiCad and assembling the BOM. Grad school is busy but I hope to have boards for the 3rd CPU design (Zeta-3) by the summer.  Ps. A programming language geared for homebrew CPUs along with lots of other helpful software (such as for generating the lookup table for the control unit) also in the works...

Here are some photos of 2nd CPU, Zeta-2:

The CPU is made from 2 PCBs stacked back to back. Headers act as interconnects.

Head-on view of the CPU. The control lines are wired into a breadboard for manual control

This side of the CPU contains the control unit. It's based around a lookup table. The backplane, flash memory controller, and a bodge board are visible to the left of the CPU connected by wire spaghetti.

Both halves of the CPU visible prior to population and connection.

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