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Neon816

A 65c816-based MiniITX motherboard.

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This project is about the design of an 8-bit/16-bit nostalgia motherboard using currently in-production parts, and designed to interface primarily with modern peripherals.

Features based on modern peripherals:
- 2 Atari or Sega-style joystick ports. Should work with 6-button Genesis controllers, and many compatible controllers are currently in production.
- DVI-D output and HD-Audio-pinout case audio connections for modern systems.
- PC-style floppy drive controller.
- ATX power connector, including support for soft power.
- SD card connector.
- PS/2 keyboard input

Also some retro and general fun:
- Commodore serial bus.
- MIDI in and out.
- GPIO header for user IO.

It's specifications:
- Western Design Center W65c816S fully static 6502-compatible 16-bit CPU.
- 1MB of main system ram and an additional 512k of video RAM.
- 128k of Flash for system ROM image.
- Lattice XP2 8000LUT FPGA for video and audio generation.

I'm aiming for a blend of 8-bit and 16-bit generation hardware and capabilities, but with a decidedly 8-bit themed user experience.  The most important thing is the immediacy of 8-bit style computers, without complicated boot sequences, memory protection, or multi-user, multitasking operating systems.  It should be easy to just power it up and start poking ports to see what happens.

That said, I plan to add some capabilities normally seen in the 16-bit generation, including some inspiration from the Amiga, Genesis, and SNES.

The current status of the project: the hardware design is complete and all parts are in house.  Currently working on initial build and test.

A Facebook group exists for those who like that sort of thing: https://www.facebook.com/groups/339934693530749/permalink/339939710196914/

  • On to Rev2 and manufacturing plan.

    Lenore Byron3 days ago 0 comments

    This is what the finished Rev1 looks like.  There were some issues around the joystick port, and I've added a couple features for Rev2.  I'm working on that now.

  • Video Generation!

    Lenore Byron04/07/2019 at 23:07 0 comments

    So the video generation is working.  DVI-D through a passive HDMI converter, to an HDMI small form factor monitor.  Also, the CPU is running and executing code, and I used it to configure the DVI encoder via I2C.

  • Building and Testing

    Lenore Byron03/23/2019 at 12:40 0 comments

    I'm working on building up the board.  The FPGA is programming nicely, I've got the UART working, and I'm building up all the missing parts.  Still waiting on a few connectors, and adding things as I test.


  • Oops decoupling.

    Lenore Byron03/21/2019 at 11:55 0 comments

    Had a bit of an issue sending a bitstream to the FPGA.  After some bug hunting, I realized it was just an electrical noise issue.  Added a bunch more decoupling capacitors and now I can program it.

    I'll fix that in the next revision.

  • It's alive!

    Lenore Byron03/20/2019 at 05:48 0 comments

    I built up the power supply sections, and they're working.  Then I tried to read the ID code from the FPGA - success!

    I guess my first attempt at BGA soldering worked out after all.

  • Reflowed my first BGA!

    Lenore Byron03/17/2019 at 21:14 0 comments

    I got my reflow oven working and attached my first BGA!


    I didn't know how well it would work, so I only attached the 2 parts I absolutely needed reflow for.  I'll hand solder things on as I need them for this board.

  • Boards arrived!

    Lenore Byron03/11/2019 at 18:08 0 comments

    The boards are here!  Now I need to figure out how I'm supposed to attach a BGA.

    Also I need to dig out a proper camera and take a decent picture.

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Discussions

rwbaskette wrote 06/08/2019 at 20:04 point

This is almost a ITX Apple IIgs!

  Are you sure? yes | no

bobcousins42 wrote 03/17/2019 at 15:42 point

I think you've got a good blend of old+new there, looking forward to seeing how you get on.

  Are you sure? yes | no

Jonathan 'theJPster' Pallant wrote 03/17/2019 at 10:42 point

I'm making something similar but with an ARM Cortex M4. Where did you get the double stacked PS/2 and DE9 headers? They look ace! Couldn't find anything good on the usual catalog retailers but the singles take so much board space. PS: Have you considered pin headers to hook up an old PC expansion plates with 2x Serial / 1x Parallel ports?

  Are you sure? yes | no

Lenore Byron wrote 03/17/2019 at 11:41 point

I think Digikey has the DE9, but I got them from Aliexpress.  Or "will get", the lead times are pretty long and I don't have them yet.

  Are you sure? yes | no

cuvtixo wrote 03/17/2019 at 06:42 point

I'm not really clear on how much you are thinking of this as a gaming device. Are you thinking of also providing a Basic language (or 2 or more?) so we can relive early programming experiences? Personally, though, I mostly remember a lot of frustration and failures to actually make anything but the simplest programs to work, so maybe not. My nostalgia is for the Apple IIe, but I don't know if your thinking of anything in that direction, though.

  Are you sure? yes | no

Lenore Byron wrote 03/17/2019 at 10:14 point

That depends on if anyone likes it!  For the moment I'm focused on the hardware and digital design, but a few people are looking at software already.

  Are you sure? yes | no

Lenore Byron wrote 03/11/2019 at 22:25 point

My old project was restored by the admins.  I'd spent a bit more time on the description the first time around, so I'm making some edits here before removing the old one.

  Are you sure? yes | no

Ekkehard Morgenstern wrote 03/11/2019 at 18:20 point

Test comment! :) 

  Are you sure? yes | no

Dan Maloney wrote 03/11/2019 at 16:30 point

Looks like it's sticking around so far. And good thing - looking forward to more details.

  Are you sure? yes | no

Lenore Byron wrote 03/11/2019 at 17:20 point

I'll be posting more details soon.  The boards are currently being delivered to my workshop today, and most of the parts have already arrived.

  Are you sure? yes | no

Lenore Byron wrote 03/11/2019 at 15:27 point

This is a repost, because the previous project just vanished without a trace.  Hopefully this one stays?

  Are you sure? yes | no

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