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 A2Z Computer 
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Joined: Sat Jan 14, 2017 7:38 am
Posts: 2

I am new to this forum. I am F4HDK, a hobbyist from France.
I would like to present my last project that I have just completed and documented here :


It is called “A2Z computer”. It is a computer made from scratch. Every part is invented, designed, and built/coded by me. I have not copied/ported existing architectures or code or software library. This is a didactic project, the goal is to learn about every part of a simple computer, from low level hardware to software, compiler.

Hardware (programmed in Verilog on a small FPGA) :
  • Custom CPU RISC 16bits (address bus 24 bits), with a custom instruction set, with Integer ALU, without interrupt capabilities
  • SRAM 2MB
  • VGA with 2 parts :
    1) Graphics 640 x 480 x 60Hz ; 256 colors; double buffering; video RAM shared with CPU
    2) Text overlaid (over graphic) 80 x 30
  • PS/2 keyboard interface
  • Serial port (interface with development PC)
  • SPI interface with a 16MB Flash chip

  • Custom basic language, with a homemade compiler
  • Assembler
  • Basic file system, and (very) simple OS
  • A text editor
  • Image viewer and map viewer
  • A car game like MicroMachines

Do not hesitate to give me feedback, or ask any question!




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Last edited by F4HDK on Sat Jan 14, 2017 11:39 am, edited 1 time in total.

Sat Jan 14, 2017 8:58 am

Joined: Tue Dec 11, 2012 8:03 am
Posts: 285
Location: California
Welcome! Very impressive!

_________________ lots of 6502 resources

Sat Jan 14, 2017 9:20 am WWW

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1783
Fantastic job, well done - and welcome!

I'll read through your project logs and have a look at your sources - should be very interesting.

Sat Jan 14, 2017 11:49 am

Joined: Sat Feb 02, 2013 9:40 am
Posts: 2095
Location: Canada
Allo. Quite an accomplishment.

Robert Finch

Sat Jan 14, 2017 3:31 pm WWW

Joined: Sat Dec 03, 2016 4:13 pm
Posts: 2
Amazing work! And welcome to the forum.

Sat Jan 14, 2017 5:51 pm

Joined: Wed Jan 16, 2013 2:33 am
Posts: 165

Do you plan on making any upgrades?

Is this computer scalable?

Sat Mar 25, 2017 8:08 pm

Joined: Sat Jan 14, 2017 7:38 am
Posts: 2
Thank you all for your feedback.

Chuckt wrote:
Do you plan on making any upgrades?
Currently, no, I consider that this project is finished.
I have lots of other projects in my "to do" list.

So unless someone wants to really use this project (as an educationnal material for example), I will not work anymore on it.
If someone is really interested, I will probably change my opinion.

Is this computer scalable?

It depends what you mean by "scalable".

* RAM and Flash : that's the easy part. It would be very easy to add SRAM and Flash. The computer has 24 address lines, and can address 16MB or RAM (minus peripherals). I could easilly change the memory module to a module on a PCB with SRAM, exactly like yours (

* peripherals : The easiest way to add peripherals would be to use the SPI bus (currently used only for Flash Memory). Adding a Wiznet Chip for Ethernet interface for example. There is still space on the veroboard for that.

* Software : currently, this CPU is compatible with... nothing. That's good for educational purpose : I had to code everything from scratch. "Learning by doing" is the main goal of this project.
But if you want to add a new functionnality, you need to code it!
So a major improvement for scalability would be to retarget an existing C COMPILER. That is necessary if I want to port existing code. A sofware enthousiast has already thought about it. And he has proved that the core of this CPU lacks too many things : indirect addressing, some operations in ALU, etc...

* CPU : so if I want to make this CPU really usable, and really scalable, the first thing to do is to make modifications inside the CPU, and add vital features : indirect addressing, ALU operations, interrupts, etc...


Sun Mar 26, 2017 5:52 am
 [ 7 posts ] 

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