Reproducing the Lisa 2 Card Stack: The CPU Card

[luminescentsimian]

I am also starting on a project to do digital RGB (i.e. CGA) to VGA on the RPi Pico, I think it is very possible, and probably even feasible for weird Mac/Lisa mono video. It’s using the logic analyzer PIO example and the PicoVGA library. Waiting on the boards, maybe have it working early 2023? Firmware always takes me longer than hardware because it sucks.

I've got some simpler code that should do the black and white classic Mac mode (512x342) that you an use as a reference. I found the PicoVGA code hard to follow because of the complexity of handling multiple modes and color depths.

GitHub - crackmonkey/macvid: Mac classic video capture and translation on an RP2040

Mac classic video capture and translation on an RP2040 - crackmonkey/macvid

github.com

There are basic CircuitPython scripts for capturing the signal and generating XGA 1024x768 from the similarly structured frame buffer and a PicoSDK C/C++ program that does both. I think I had to use the PicoSDK because CircuitPython doesn't have a way to do custom interrupt & DMA handling needed to feed between the input and output PIO programs.

 

[DosFox]

Sweet! It's amazing to me that there are still un-dumped ROMs for parts of the Lisa at this point. Alex is looking for a quick-boot ROM for the Sun SCSI card that apparently hasn't been dumped, and the firmware for the Sun MFM HD was un-dumped until, well, now I guess.

Ah I just checked my ROM archive, the only Sun SCSI ROM I have is 341-8007, which I'm guessing isn't the quick boot ROM!

 

[LeadedSolder]

I've got some simpler code that should do the black and white classic Mac mode (512x342) that you an use as a reference. I found the PicoVGA code hard to follow because of the complexity of handling multiple modes and color depths.

This is excellent, I'll take a look once I start delving into this. I haven't done the "input" side yet, only some simple test patterns on the output.

 

[warmech]

You know what's generally a prudent and conscientious methodology for producing a fairly complicated four layer PCB the size of a dinner plate?

MAKING SURE YOUR DAMNED ICs ARE POWERED.

That... is an expensive mistake, lol. And possibly the reason why the PCB has been running into issues.

 

[DosFox]

You know what's generally a prudent and conscientious methodology for producing a fairly complicated four layer PCB the size of a dinner plate?

MAKING SURE YOUR DAMNED ICs ARE POWERED.

View attachment 10094

View attachment 10095

That... is an expensive mistake, lol. And possibly the reason why the PCB has been running into issues.

Oh god! Easy mistake to make I guess? Also relatively easy to repair hopefully

 

[DosFox]

You know what's generally a prudent and conscientious methodology for producing a fairly complicated four layer PCB the size of a dinner plate?

MAKING SURE YOUR DAMNED ICs ARE POWERED.

View attachment 10094

View attachment 10095

That... is an expensive mistake, lol. And possibly the reason why the PCB has been running into issues.

Did you ever get the chance to patch and retest your CPU card?

 

[warmech]

Did you ever get the chance to patch and retest your CPU card?

Yep - Alex has my card at the moment and got a chance to bodge power and ground to U5A this weekend. It now boots into LOS successfully! LisaTest does report an issue with the error logic, apparently, but it's not enough to interfere with the system actually operating. Now that we've stomped that bug, all focus is on figuring out the error logic issue and then it's done!

 

[DosFox]

Yep - Alex has my card at the moment and got a chance to bodge power and ground to U5A this weekend. It now boots into LOS successfully! LisaTest does report an issue with the error logic, apparently, but it's not enough to interfere with the system actually operating. Now that we've stomped that bug, all focus is on figuring out the error logic issue and then it's done!

That is amazing news!!

Really hoping that error logic issue is something simple - at least it's not getting in the way of booting LOS.

Now all that's left is to test the ram card and you've got a complete stack Lisa stack!

 

[LeadedSolder]

That’s very exciting news! Looking forward to building my own board stack one day.

 

[warmech]

Okay! After getting some readme stuff written up, here be the Lisa hardware repo on my end. Alex's is here, and he's got all the other PCBs. I need to wrap up the RAM cards and get them posted, which I may try to do this weekend over the holiday. The RAM additions will include three separate PCBs: the stock, OEM card with 512K of parity RAM over 72 4164 DRAM ICs; an LRambo-modded OEM card that's equivalent to a 2MB AST RAMStack card; and a 2MB parity-based SIMM version.

Once those are up and tested, there are a couple minor boards left (the LisaLite and the video board) and the Lisa hardware can be considered complete. After the LOS source release at the end of January by the CHM, the Lisa will have effectively become an open-source machine. I cannot express how happy I am that that is now the case. Alex and I have one more trick up our sleeves, though... more on that later.

 

[DosFox]

That is amazing to hear, now the race is on to see who will be the first person to make a completely brand new Lisa in almost 40 years!

 

[Paralel]

Truly a breathtaking accomplishment. Kudos to all involved, your hard work will ensure that a piece of computing history will have new life and love in the 21st century.