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  • Writer's picturerehsd

A Start to Video Output for My 65816

Updated: Feb 20, 2022

For my "VGA 2.0" circuit, I am going to try and get 320x240x1byte running. To support this, I will be using three IDT7007 dual-port SRAM ICs, giving me 96K x 8 bits. Each SRAM IC has 68 pins (ouch). To give me a chance of wiring this up, I am looking to build a PCB that is essentially a memory card for the video circuit. Possibly, I can later expand the card to include the full VGA circuit.

This will be the first 6-layer PCB that I have ever tried producing, so this could be interesting. Something like this:

6-layer PCBs don't come cheap, and there's no fixing signals on the inner layers. I am trying to keep things pretty basic with this card. I am connecting the address and data lines of the three SRAM ICs and exposing all other pins via headers on the PCB.

Wish me luck!


u/gfoot360 suggested a stackable design, which is a great idea. Based on that suggestion, I'm looking at something like the following. With a 4-layer design (inner GND and VCC layers), a set of five boards is only $8 USD. An additional plus to this design is that I can stack as many chips as I need to increase total memory capacity.


Boards ordered (very close to the stackable design posted above). I'll test the physical stacking aspects in a few weeks after I receive the boards and sockets. More to come.


The physical aspects of the design are looking pretty good.

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Joe Plocki
Joe Plocki
Feb 04, 2022

I've only been to 4 layers, and then, only because I ran traces so tightly that my ground plane couldn't reach some of the pins in the middle of the board (whoops). Instead of retracing, I added 2 more layers, and put VCC/GND planes on the inner layers. Oddly, I did have to bodge that board, and having the signals on the top and bottom layers is the only way I would have been able to make it work...

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