*** UPDATE ***This Project has been fully reloaded! See the final version come to life here...https://www.atomiczombie.com/vulcan-74/Greetings to all 8 bit hackers!Just wanted to make a brief introduction and start a kind of blog on my new 6502 project.
Like many here, I was introduced to computers in the early 1980's, and have dabbled in electronics and programming at a Hacker's level ever since! Remembering the good ole days, sitting in front of that glowing green screen of my PET-4016 brings back images of a better time, a time when a pixel and a byte were worth something, and a time when you had to hit the bare metal, talking directly to the machine in order to make your programs work.
These days, you can purchase a $20 board level computer that runs Linux at 400Mhz, and drop premade code into the flash in order to do just about anything without really knowing anything but how to click a few buttons. Where is the fun in that?! A Raspberry-PI is certainly a powerful piece of hardware for the money, but in my opinion these things do not fit into the electronics hobby zone, nor do they teach much about hardware and bare metal programming. Just a computer without a box.
I will admit to going down this path myself, as my last project was a VGA video generator strapped to an AVR. Coding in Verilog for the very first time, I was able to make my project work in one afternoon! With a 1 million gate FPGA capable of running at 400MHz and a hardware synthesis tool that almost thinks for itself, I soon realized that this hobby was getting boring! What was going on under the hood?
So my goal is to devolve back to the 1980's and build a retro game system.
Now when I say "Retro", I don't mean some Arduino-thingy running Pacman, I mean a complete system built from the gate level using ONLY hardware that was available in 1984 during the time when the C-64 Animals sat in a room smelling of reefer, staring at hand written schematics made with mostly 7400 logic components. Yeah, these were the days where true Hackers needed more than a set of trendy dark framed glasses and a premade $15.00 embedded kit to call themselves Hackers!
Ok, so now that I have explained my reasoning (or lack thereof) for starting this project, let me explain what my goals and rules shall be.
The Rules...- Only 7400 logic gates that were available in the 1980's may be used. Chips like 7404, 74688, etc.
- All chips must still be available at Digikey and easy to source. So only 74HC logic will be used. No 74LS or e-bay items like 74LS188 may be used.
- The only processor to be used will be the 65C02 from Western Design Center. This is because the chip is still available and because Bill rocks.
- Although I must only use 1980 era parts, I am allowed to used today's variants. So 74LS is replaced by 74HC (but not 74AC), and all SRAM can be 10ns speed.
- All parts must be DIP so they can be used on a breadboard initial prototype. I will bend the rule only in the case of the SRAM, and use SOJ parts, which are certainly hand solderable to a DIP socket.
Absolutely no modern parts such as AVRs, FPGAs, GALS, or custom ICs can be used. If the technology wasn't available to the Vic-20 crew, then I can't use it.
- The project must first prove itself on a breadboad. From there it will be hand wired onto perforated board. With an estimated chip count of 200, and a speed of 20MHz, I know this will be fun!
The Goals...- Video must be perfectly stable VGA, putting out 256 colors at a resolution of 400x300 using an 8 bit color space divided into RRR-GGG-BB.
- Video must include full 256 color 400x300 bitmapped screens with a seamless double buffer for high speed animations and high detailed images.
- The GPU system will include a high speed (20MHz) blitter system capable of dealing with moving variable sized bitmaps from a dedicated 1MB memory bank to the back buffer independent of the 6502 CPU. The entire GPU must be made ONLY of 7400 logic parts.
- The sound system will be minimum 4 independent digital sound channels, and include its own 1MB independent sample SRAM. Much like the Amiga, the sound system is independent of the CPU, and again all made with 7400 logic parts.
- The completed system must be capable of impressive games (Amiga quality), not just some simple tile engine. All games will load only from an external EEPROM (cartridge) via onboard 7400 logic based loader. No external processing will be allowed.
- The CPU will be a 65C02 only. No 65C16, as this is too new for my system! The 6502 will run at 16MHz minimum, using whatever IO decoding tricks I see fit. Bus pirating illegal opcodes, etc. Prelimanry tests have shown stable operation at 20MHz using a ROMless system running from 10ns SRAM.
So that is my introduction to this great group!
I only hack at this stuff on odd weekends or rainy days, but I will post updates as Vulcan-74 takes life. No doubt these are lofty goals, but I know enough to put this together, but not so much as to listen to reason! Let the fun begin.
Here is the "Mother of all Breadboards", where my project will become self aware...
Oh, and the reason for the name is because of the pure 74xx based hardware. Logical, Captain?
Cheers,
Radical Brad
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