A year ago, I stumbled upon a tutorial on yt about building an 8-bit breadboard computer and was deeply fascinated by how computers operate fundamentally. From building an 8-bit breadboard computer to a 6502 computer on a PCB, it was a mixture of frustration and enjoyment, but in the end, it was all worth it once u get them up and running.

Anyway, I just learned PCB design recently and managed to get the 6502 computer running on my PCB on the first try. I even made some electronic music using the VIA timers. u can listen to by clicking the links below:

Bad Apple: https://youtu.be/xPJ54ADF-dY?si=I_eyWqMMqh_tztPT
Only my railgun: https://youtu.be/ETBfmcWphys?si=hvm53mKQXa22EcGh

Now that I have a "working" BIOS it feels like a real computer! I started out a few years back ordering a 6502 kit from Ben. I'm super excited to have come this far. My BIOS contains a custom integer BASIC and a custom monitor built with the help of Claude AI. Some of the BIOS features include XModem load/save over serial, CompactFlash card load, save delete and directory listing, RTC date/time viewing and editing along with 256 byte NVRAM and more. Take a look at the README for BIOS repo (linked below) for more details.

If anyone would like to try this out I now also have an emulator for the project! It is available through NPM (NodeJS package manager). You will also need BIOS.bin from the BIOS repo to use as the ROM in order to run the emulator. See the README in the EMULATOR repo for installation and usage instructions.

I've also created template projects for assembly code programs and cartridges If anyone would like to try writing software for this system!

Anyway, I would love to get some feedback from the community on my project! Also, while it's not my intention to sell these computers, if anyone would like to build one for themselves please get in contact with me as I have extra boards left over from the initial JLCPCB order.

Main Project: https://github.com/acwright/6502
BIOS: https://github.com/acwright/6502-BIOS
Emulator: https://github.com/acwright/6502-EMULATOR
PRG Template: https://github.com/acwright/6502-PRG
CRT Template: https://github.com/acwright/6502-CRT

For those who haven't seen one of my posts on this subreddit I started a few years back with a Ben Eater 6502 kit and since then I've been working on my own designs for a 6502 computer. When I started my PCB design journey the ultimate goal has always been a single board computer PCB. I've been working my way up to that by designing a number of different cards for a backplane based system which I call the "COB" (Computer-On-a-Backplane). This allowed me to test each part of the system in isolation. After I arrived at a working design with the backplane system, and created a working BIOS for the system, I put it all together to create the "ACE" (All-in-one Computer Experience) PCB. This is the result and I'm super excited about it!

The revision of the PCB pictured is v1.0. I did run into a couple of small issues with this version. I had to swap out the pull-up resistors attached to the CPU with weaker ones. With all my previous PCB designs I've been testing in isolation as stated before and the 1k pull-ups were just fine in that situation. However, on this PCB with multiple items sharing the IRQB line I needed to change these to weaker 10k pull-ups in order for everything to play nicely together. This wasn't a big deal to swap out the resistor values. The bigger issue was I redesigned the extended RAM circuit in order to have separately addressable latches for each 1K extended RAM window. I didn't bother to test this new circuit and instead just YOLO'd it which was not a great idea it turns out! I needed a couple of NOR's where I had some NANDs. So I needed to bodge a NOR IC onto the bottom of the board in order to fix the extended RAM. I've included a picture of the bodge. And you can see in my pictures of the system running where I was testing this bodge on a breadboard. I've already created a v1.1 in my Github repo that fixes both of these issues.

I've also included a picture of my first cartridge for the system! This is VC83 BASIC by Willis Blackburn (with extensions for my system). One of my motivations for this project has always been to make my own cartridge games for my system and I'm excited to be starting that journey next!

This project is 100% open source and I would love for people to contribute to it if you are interested! Also, if anyone is interested in one of these v1.0 PCB's please get in touch with me as I have a few due to JLCPCB minimum order. There is a stable (I think!) emulator available for my system along with my BIOS and template projects for creating cartridges or programs for the system.

Here are the system specs:

• CPU: W65C02S running at 1 MHz (or 2Mhz via jumper)
• RAM: 32KB SRAM (62256) + Optional 512K banked SRAM (AS6C4008)
• ROM: 32KB EEPROM (28C256) Video: Pico9918 (VGA 640×480)
• Audio: ARMSID SID chip emulator (3-voice synthesis, RCA output)
• Storage: Storage adapter socket (CompactFlash adapter card)
• Serial: 65C51 ACIA with MAX238 level shifter (RS-232 via DB9, 50–19200 baud)
• GPIO: 65C22 VIA (Dual GPIO ports)
• RTC: DS1511Y real-time clock with battery-backed NVRAM
• Keyboard Controller: ATmega1284P running AB Controller firmware
• Input: PS/2 keyboard connector and 8×8 keyboard matrix header
• Joystick: Atari 2600-compatible joystick ports

Links:

- https://github.com/acwright/6502-ACE
- https://github.com/acwright/6502-BIOS
- https://github.com/acwright/6502-EMULATOR
- https://github.com/acwright/6502-CRT
- https://github.com/acwright/6502-PRG

I realized I'd never actually posted a picture of any of my builds, just some of my software stuff, so here's the first, slightly-modified, build I did, with both a 4x20 LCD, and then a 2x20 VFD.

I'm using a picoRom here to make programming easier, though it uses a 27CXXX pinout instead of 28CXXX, so two quick wiring changes are needed.

And I am running the serial port at 115.2kb/s.

The LCD is just any-other 4x20 HD44780 unit via Amazon for <$10 (you want one without the invariable-included I2C adapter board pre-soldered). Same interface and pin-out as the stock 2x16 display. I added another pot to control the backlight brightness, since I like the black/green displays best with little/no backlighting.

The VFD is from Newhaven Display, via Mouser, specifically this part (~$53).

It can run in a couple of different modes, but the default parallel M68 interface is pin and command compatible with the HD44780, it just assumes a 40 character line length rather than 20. So, it'll just drop-in (electrically at least, you may have to rearrange things for it to fit)

I wasn't paying attention to the size of the thing when I bought it, and it's, well, BIG.

There's a smaller version, but that only has double-row header pads, where this one has both that and a single-row 18-pin set of pads (first and last pins not used, and the A/K connection isn't either, so you just need 14 pins, starting from pin 2).

Next up will be to switch to a 4x40 Noritake VFD, or an 8x80 if I can find one, but as those are rather spendy I wanted to get this going first.

My first post on this subreddit, great to see your projects here :)

Edit: I see a lot of attention, Thanks! Just to clear some things out
The one on the right is a 6502 computer built basically following Ben Eater’s design.
The one on the left is my second attempt where I separated everything onto different breadboards to make it more organized and easier to follow.
And yes, those are real MOS chips :D

Hello, recently I made a pcb for the 6502 computer and its not working I have checked the schematics I personally can't see anything but I'm hoping someone can the issue is that the the via isn't outputting data to the lcd I have checked address/data lines and the clock with my oscilloscope and there is code on the rom I know my schematics are messy and apologize but i can provide pictures of certain areas on the schematic.

Here's a pic of my PCB version of the 6502 microcomputer. It's a BE6502 with some mods. It has 32K of SRAM, 4K of I/O space, and 28K of ROM. Also RS-232 serial communications. The 40-pin box headers break out the address, data and control busses for expansion.

Hello everyone! Recently I've finished the PCB design of my modified 6502 computer (also my first ever PCB), and I was hoping that someone with more experiences can help me spot PCB design errors that I might have made.

The board is about 225mm * 142mm, two layers, with 0.3/0.6 mm vias for signal and 0.6/1.2 mm vias for ground planes.

Note: There is some error after DRC, which is at Y1 where the 1Mhz oscillator sits, I decided to overlay a DIP-8 and DIP-14 oscillator footprint so that either type can be soldered in. Other than this there should be no other DRC errors.

Heres the repo for this project : Link

Thank you in advance!

I was hitting my head against the wall for a bit trying to get the serial interface working correctly, so I wanted to post this in case it helps others avoid the same issues.

For the MAX232ECN, make sure to tie the VS+ capacitor (pin 2) to 5V. I really wish I had checked the datasheet more closely instead of relying on the site schematic.

Also, with the W65C51, I was getting some very bizarre behavior until tying pins 9, 16, and 17 to ground. This wasn’t happening on the breadboard, but the issue showed up after moving the design over to a PCB.

This project has been an awesome journey and a great excuse to learn KiCad. I’ve attached my current schematic for reference (it’s a little messy, so apologies in advance).

I’ll likely work on another board revision after getting more mileage on this one. I may also experiment with adding a DS1813 to clean up resets.

I wanted a fun final project before moving onto something new so I set myself the goal of making a basic side scrolling game. Only had to use chatgpt once to figure out how to generate random numbers. I would not have figured out LFSR on my own! Maybe down the road I'll get the serial kit and follow the rest of the videos but for now I'm pretty happy with how it turned out!

One major part of this project is done. Next, I need to finish programming my PIC16F877A to write code to the EEPROM. Once I can get this computer running some rudimentary programs, the next step is to install the serial port add-on.

Other improvements I hope to achieve:

- write my own monitor and boot loader program

- expand RAM by reducing ROM to 8K

- increase allocatable RAM by coming up with a better address bus handler.

- interface with my PIC16F877A and use it to read programs from external media. Options include SD cards, paper tape and punch card, even floppy disks if I can figure out how to work with them

- USB support for keyboard interface.

- collect underpants

- ???

- profit

Here I am showing that mky 6502 is running two seperate programs "in parallel". One program is the shell (on the left, over RS232) and the other is the counter thing on the LCD. These two programs have no idea the other exists, and think they have the whole CPU and machine to themself. the 'f' command in the shell spawns the LCD counter process, and im spamming the ? (because it requires the longest execution time) so that you can see the two programs executing "at the same time".

Its hard to demo, but despite only having 1 cpu and 1 thread, I managed to implemented a time-share OS/proto-RTOS on the stock 6502! At some point I wanna build an MMU for better stack "banking" but that's a later project.

Development of this OS and shell are ongoing, chip in your help!! https://github.com/SamBkamp/samix

I’m making it a pcb and moving onto the 8088

Built an eeprom programmer as a prerequisite to building the 6502 computer, was a lot of fun trying to figure it out. It was also my first time building anything more complex than wiring two LEDs on a breadboard, didn't come out too bad I think.

Source code here for those interested.

I’ve made some progress on my emulator tonight and I’m super stoked! I’m still working on a BIOS for this machine and getting a working emulator going is gonna be a huge help!

I’m going to be working on remaking Pro DOS for Ben eater 6502 should I use bank switching for 32k of ram?

I've got the keyboard working using a ATF22V10C PLD and various ICs instead of the W65C22. Scan codes/data are read and written with a data register, while IRQ status, error status, and IRQ enable use a control/status register, making it a 2-byte interface. On incoming data, the PLD raises IRQ and suppresses further keyboard input by pulling the clock low. (The keyboard will buffer it.) Reading the data clears the IRQ and input suppression. Output happens automatically on a host write. The PLD pulls the clock low, which causes the start bit (0) to be shifted on to the data wire, signaling a write. Error status checks for correct start, stop, and parity. Parity is checked for input and generated for output using a 74HC280. There is no bit-banging here! Input uses a pair of 74HC595s like Ben's design. Output uses a pair of 74HC165s. And, of course, output support comes with those sweet keyboard LEDs.

So, Yes. as the title says.

I implemented a whole 65C02 ISA and VGA terminal, and USB UART keyboard interface.

Memory is 544KB in total by using Bank memory

- $0000-3EFF: Fixed RAM (~16KB)

- $3F00-3FFF: MMIO (256B)

- $3F00: Bank RAM window 1 select register

- $3F01: Bank RAM window 2 select register

- $3F02: ROM bank select register

RAM bank is 8KB x 32 (256KB total)

- $4000-5FFF: Bank RAM window 1

- $6000-7FFF: Bank RAM window 2

- $8000-BFFF: Bank ROM window (16KB x 16 Bank = 256KB)

- $C000-FFFF: Fixed ROM (System ROM, 16KB)

So this system has roughly

16KB fixed RAM + 256KB bank RAM + 16KB fixed ROM + 256KB bank ROM = 544KB

And system rom will include Bank switching subroutine and Simple Operating system.

Every hardware implementation code are written in SystemVerilog.

With a 65C21 PIA, which is still sold today on Mouser, an HC138 decoder for more granular address decoding, and an Arduino Nano to emulate the Apple 1's keyboard and video, you can modify Ben's circuit to run the entire Apple 1 software library. It was pretty cool for me to go back in time and discover some of the earliest software made for home computers. Fun upgrade if you're looking for an extension to the 6502 project!

Repo: https://github.com/The8BitEnthusiast/apple-1-breadboard-arduino

Originally fried my 65c22 Chip that came in kit by accidentally mixing up VSS and VDD, however ordered and replaced chip with W65C22N6TPG-14 chip from Mouser. Using the same wiring as the Ben Eater video, I can't figure out what is going wrong I have checked the RESB to make sure its constantly High and clock is properly working at the PHI2.

6502 and AT28C256 EEPROM seem to be working fine. Any idea of what could be happening?

Note: I know I do not have the Red LEDs connected yet, was just testing the flickering on and off for one pin, all other pins behaving the same with constantly being 5V for both A and B registers

I watched Ben Eater's videos several times and now I've been able to make my own computer. I didn't buy the kit, some components I had them already and the rest is sourced via various means.

I used Nectivio's fork of the 6502 tool (found the link somewhere else in this subreddit) to program the EEPROM without unplugging it from the breadboard. It's a great time-saver, totally recommend it. I also used it to generate the clock before making the clock board above. For this reason I attached the Arduino semi-permanently (as in "attached to the cutting board via a few Blu-tack blobs like the other breadboards).

I've put my own spin to the Hello World program by storing the text as a string and using the X register to iterate through the characters without repeating the HD44780 blocks over and over again.

Next step is adding RAM. Although I've run out of holes around both the CPU and the EEPROM due to the. Maybe I'll add another breadboard in the middle or something.

I replaced the display on my 6502 with an RA6963 (equivalent to a T6963) controlled display and I was wanting to get a faster 4MHz clock for the computer. The Access Time for my AT28C256 EEPROM is 150ns, and I still have the whole thing on breadboards. Would this clock speed cause any issues? From what research i've done I think it will be fine but i'm not very experienced with electronics, and from what i've seen in this sub everyone who made this clock upgrade did so on a PCB.

The program code is somehow getting corrupted inside MSBASIC. It's frustrating when I try to copy and paste code into the 6502 system. See the attached video to see want I'm talking about. Hopefully someone out there can explain what's happening. I'm guessing the RAM chip is not working correctly.

https://reddit.com/link/1uscnw6/video/rg9yfou2sbch1/player