An interesting pair of projects over on retrobrewcomputers, using a 128k SRAM socket as the interface to a VGA-style subsystem:
VGA Expansion for 128KB RAM
VGA Piggybacked on RAM, An Experimental Prototype



(These are by plasmo, who is also here, and mentions the idea in passing here.)

Piggybacked VGA on RAM was discussed first on this forum here. I like the compactness and visual effect of stacked components so I redesigned the VGAxRAM last night as 2 small stacked boards; this morning I changed my mind. What changed my mind was the idea that pairing a CPLD with RAM can add the keyboard function making the 2-board stack a fully standalone computer.

I need to think more about it, but as a general concept replacing existing DIP32 RAM with an equivalent SMT RAM + CPLD may enable a number of I/O functions such as serial, I2C, SPI, WS2812B LED, logic analyzer, etc...

Bill

Thanks for the extra back link! I hope you agree it's nice to have a thread on this project (or these projects...)

I appreciate you providing links to older posts to remind people, especial newcomers, of existing discussions here on 6502.org as well as other forums.
Bill

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Only took me 6 months to build up this RAM board with SMT RAM and EPM7064S CPLD. The original concept is removing the existing DIP32 RAM and plug this board into the DIP32 socket. This board implements PS2 keyboard interface while stacked above this board is a text-based VGA board. So the two-board stack performs the function of PS2 keyboard and VGA interface using a RAM as expansion bus. That's all well and good, but I'm now intrigued by the general concept of using DIP32 RAM as an expansion bus to implement a number of I/O functions. The board stacked above can be other I/O boards.
Bill