Alright, Mark... I do understand and sympathize with your position. And I didn't mean to come across as though I expected you to re-engineer the whole project all at once.

But some piecemeal changes may bear consideration, particularly in regard to signals that need to get input by the CPU. Much ...

Nice update, that keyboard must have been frustrating - I don't like soldering things that don't want to be soldered!

The counter solution is good too, it sounds like you're building a solid foundation there. I like the 175 with its inverted outputs and common clock. I think you mislabelled some ...

So I’m planning to latch the address and data lines on CPU write, and from there write to a bunch of output latches. Sounds like a non-trivial alteration. :|

Would you bother with all this extra work if the fanout issue were magically solved? Because I suspect it easily can be, if you'll just ...

Update 2023-09-16: Keyboard hacked, NVRAM backup, Planning soldered breadboard, Potential fanout issues, Improved clock module

Keyboard hacked:

To avoid using USB and any associated CPUs, and to get lower keypress latencies and better overall control of the keyboard access, I’ve bypassed the ...

I'm thinking I will also need a smallish (7-10ns) delay when I get to higher speeds, and using higher speed clock sampling tricks will not be convenient. So I recently bought but have not tested a DS1100Z-20+, which is a relatively cheap chip that has multiple-of-4ns delays up to 20ns. I'd love to ...

Update 2023-09-06: First font demo on LED display panel

Okay, turns out I had time this week. The frame buffer is working great, and adding that did not compromise the CPU’s 12.5875 MHz clock speed. I’ve put together some font drawing routines and made a little demo showing the 5x7 printable ...

This is looking very usable -- quick work! This is encouraging me to go vertical and learn CPLDs.

Update as of 2023-09–01: Video framebuffer working, surgery on CPU module

First, for future upgrades:
Wow, evidently there are multiple much finer pitch (1.25mm / pixel) LED panel modules at reasonable prices. Do a Google search for [HAIHUANG P1.25 Indoor Led Matrix Module, (Size: 320x160mm) RGB ...

I have an Apple II style graphic design where W65C02 shares video RAM at different phase of the clock. I was able to achieve 12.6Mhz for 6502 cpu clock, half the VGA clock. Unfortunately I use CPLD for logic which is fast, but not consistent with your locked room requirements.
http://forum.6502.org ...

If you or anyone can point me to existing art on interleaving video and CPU access to an SRAM at high clock speeds, that would be great! Others here are a lot more versed in this than I am - I went with dual-port RAM for my VGA circuit. However, "The CRT Controller Handbook" by Gerry Kane is an ...

I've built several different 6502 systems like that. I think my main advice is not to interleave access to the CPU's main memory in the fashion of old 8-bit computers, especially if you need higher clock speeds - it is better to have a separate pool of video memory with its own buses, and only let ...

A couple of unexpected pixels: the first few leftmost of the red block, and the bottom right pixel. Are they the ones you mentioned as damaged?
Yes, the upper left side as pictured is where a fair number of SMD pixels got knocked off before I got the module, the the lower right is where the SMD ...

This is really cool. I like how you're taking things a different direction from a lot of hobby projects, particularly with that LED panel for output, and manual entry for input.

The alternate design choices I think come from the combination of doing a fairly extreme version of bootstrapping (no ...

Update 2023-08-28: LED panel timing circuit

Looking at the back of my LED 128x64 RGB panel, I see the critical chip type is labeled ICND2038S. Google search gave this data sheet:
https://olympianled.com/wp-content/uploads/2021/05/ICND2038S_datasheet_EN_2020_V1.6.pdf

ICN2038.pdf
This is written ...

The hexadecimal keypad is definitely a step up from toggling switches for binary input! I'm really glad I took the time to design and build that. I would probably make it a bit easier to use given my experience now putting in the better part of a kilobyte of machine code...

On bootstrap loading ...