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Huh, the IIsi is actually wired to accept a 4 MB onboard RAM array on the same footprints. The extra A9 address line is wired up from the MDU to the RAM even though it’s not used. Alright, I’ll do it. We’ll see how it turns out.

The Mac IIsi motherboard is wired for a 1 MB onboard RAM array using eight 256kx4 DRAM chips or a 4 MB RAM array using eight 1Mx4 chips. After discovering this on my broken IIsi, I was able to simply replace the eight RAM chips with larger 1Mx4 RAMs (e.g. KM44C1000, M5M44400, MT4C4001) and get 4...

Boards are on the way to you, Garrett. Wow, that was fast! I picked slow shipping though so it might be a while before the boards get to you. I'll message you the tracking number

Timing diagrams are finished, I think. Gotta translate them into verilog and then I can simulate to make sure my verilog is as expected. Maybe I should write a program that takes the WaveJSON format I did the timing diagrams in and outputs verilog for simulation. Hmm... Yeah that's probably my...

Yeah I think the IPEX connector antenna is more reasonable but I am trying the "sticking out the back" approach to see if it's workable. I did reserve room on the board to move the ESP32 module inward and cut the board off at the bracket just in case the current approach doesn't work so well...

Has anyone tried piggybacking another set of VRAM chips on top of the ones already mounted on the motherboard? On the 840AV, most of the signals are shared between the soldered VRAM and expansion VRAM. The only different pins are separate /RAS and /SE lines on the CIVIC video chip which are...

Great! These keep rising in price. I was able to get em for a buck or two each back in 2015. Now they’re like $15 on eBay. I’m gonna make some when I get the chance.

Oops, forgot to respond to this. Yeah, the issue is with chipsets that leave a row open (i.e. /RAS asserted) and then let the CPU access other devices. On the SE/30, for example, you can put EDO RAM in with no problem. (Not that anyone really makes 30-pin EDO SIMMs.) The chipset always brings...

Just ordered a few boards! Yeah, the wider design was the right way all along, that way it'll go in the chassis rails as well as guide the insertion of the card into the motherboard. Obvious in retrospect but the card is so short that I thought it wouldn't rise up to the chassis rails at all...

I think the board is done! Also attached is the most recent schematic. Source for the board is available on GitHub: https://github.com/garrettsworkshop/NuBus-ESP32 Now onto the software phase. I think first step is to begin the utility on the Mac to select your WiFi network. ESP32 makes...

Here's one of my favorite resources on car dynamics which I read and re-read many times as a Honda-obsessed teenager: https://www.autozine.org/technical_school/tech_index.html The author, Mark Wan, describes the site best himself: The material on this site basically taught me the principles...

Wow, this is an amazing repair. I usually tape down bodge wires against the board with kapton tape. I always thought that was a fairly low-profile solution. I had never considered laminating the repair into the board! Amazing... I have to try your technique of building up the mask goop next time...

Alright actually I have changed my mind... you're right, it should just be rectangular:

Here's the latest progress on the board: Almost done, basically I've just gotta pretty it up some more. I've put the screw holes in the same places as on a NuBus card but the slots next to the holes have different dimensions to accommodate the larger width required for the 3d-printed...

Alright I'm gonna order the boards!! Then I can circle back to the WiFi card and the SE accelerator.

Hmm well the required dimensions are actually somewhat more dramatic... It's 8.58 mm (2.7 inches) at the bottom, same as the width of the original. Looks kinda crazy though. Am I worrying about it too much? Should I just go ahead with these dimensions? Edit: Garrett says it looks like a...

Something along the lines of this?

Hmmmm, should I make it wide on the bottom and taper on top then? IMO that would look less stupid than the other way I showed in my last post

One thing before I send the board to be fabbed. The card is short so there is no apparent need for the board to "slot in" to the slots on the sides of the connector box and I don't even know if the dimensions for that will be the same since we're using the right angle connector: But the card...

Great. No more of this two-connector crap! Just put in an order for 112 of the RAM chips and 60 of the connectors. Just gotta take a few more measurements of the Mac Classic before sending off the board to be fabbed.