| Click here to select a new forum. |
| Reverse-engineered Classic II |
Posted by: btb on 2025-05-25 14:58:08
I depopulated (mostly) and reverse-engineered my badly-bombed Classic II, and here is the result: https://github.com/btb/ClassicII
My schematic, as a PDF. I also made corrections to the Bomarc schematics as I went along.
The PCB is fully layed out in KiCAD, and I'd like to do a "reloaded" version, but this isn't it yet, as I want to include some more features, such as:
- footprints for both older and the newer revision ROMs
- Wider pads for the electrolytic caps to better accommodate tantalums
- 2032 battery footprint
|
Posted by: cheesestraws on 2025-05-25 16:34:13
Good stuff! Well done. |
Posted by: finkmac on 2025-05-25 17:36:43
excellent. you deserve praise for these efforts. |
Posted by: Andy on 2025-05-25 19:31:31
Wow that's super cool! Thanks for putting in the work and sharing 💜
I want to include some more features
We have to fit in an LC PDS connector in here somehow 😉 |
Posted by: btb on 2025-05-25 20:33:51
Wow that's super cool! Thanks for putting in the work and sharing 💜
We have to fit in an LC PDS connector in here somehow 😉 Hey, if it’s plausible ill do it, haha |
Posted by: JC8080 on 2025-05-25 21:42:26
Great work. Those schematics look nice, maybe there is hope for my Classic II after all! |
Posted by: frontein1 on 2025-05-25 22:34:04
Wow this is fantastic work!! |
Posted by: robin-fo on 2025-05-26 00:35:40
Your work is incredible valuable for the community! Thank you so much! |
Posted by: robin-fo on 2025-05-26 00:37:00
We have to fit in an LC PDS connector in here somehow 😉 Better just add Ethernet circuitry without the big connector… |
Posted by: Boctor on 2025-05-26 04:05:15
It looks so beautiful that I'm already dying to see someone talented at drag-soldering put one together. These things always make a great visual aid to schematics, and seeing as you've gone back and patched the Bomarc ones, it's a win-win. Whether someone needs bodges and trace repair or a brand new board, you've single-handedly brightened the futures of countless Macs, so thank you! |
Posted by: max1zzz on 2025-05-26 04:07:56
Very nicely done! I guess now I have no excuse for relegating that pile of CII boards to donor status 🙂
On you comment on github of not knowing the ASIC pinouts, have a look at the LC II schematic: https://www.macdat.net/files/pdf/apple/schematics/apple/lc_ii.pdf
As the pinouts for the main ASIC between the LCII and CI are pretty much the same (though not exactly) it should be a decent guide |
Posted by: nathall on 2025-05-26 05:39:42
The Classic II deserves preservation. It’s the Mac that got me back into the Macintosh. If I had to be buried with a compact Mac, it would be the Classic II. |
Posted by: robin-fo on 2025-05-26 05:42:39
I have a similar affection to the Performa 200, since I saw (many many years ago) a video on YouTube where some idiot shot on one… Poor thing.. 🥲 |
Posted by: nathall on 2025-05-26 05:52:50
I have a similar affection to the Performa 200, since I saw (many many years ago) a video on YouTube where some idiot shot on one… Poor thing.. 🥲
Simply sacrilege. 🤬 |
Posted by: btb on 2025-05-26 08:34:59
Very nicely done! I guess now I have no excuse for relegating that pile of CII boards to donor status 🙂
On you comment on github of not knowing the ASIC pinouts, have a look at the LC II schematic: https://www.macdat.net/files/pdf/apple/schematics/apple/lc_ii.pdf
As the pinouts for the main ASIC between the LCII and CI are pretty much the same (though not exactly) it should be a decent guide Thank you!
Oh wow, I didn’t know that one was available, that should be pretty helpful! |
Posted by: cheesestraws on 2025-05-26 08:41:06
Better just add Ethernet circuitry without the big connector…
clone of That Awful Colour Graphics Card built in tbqh |
Posted by: btb on 2025-05-30 00:42:09
I guess I can't edit my post. I've made a bunch of changes, and the link to the schematic is now https://github.com/btb/ClassicII/blob/main/ClassicIIRevB/ClassicIIRevB.pdf |
Posted by: Andrewski007 on 2025-06-11 18:52:05
Out of morbid curiosity, would it be theoretically possible to add a PDS slot to a classic II, even externally (not mounted on the board)? |
Posted by: btb on 2025-06-11 21:07:38
Most of the pds slot signals from similar machines are straight off the cpu, so no problem connecting those, however I think one or two are handled by the V8 or other ASICs - not sure if they are strictly necessary, or if they might actually be already present on some unused EAGLE pins. Someone more expert than me might have a clue |
Posted by: Arbee on 2025-06-12 15:57:56
Comparing the Classic II and LC II schematics, the major thing is that EAGLE lacks the SLOTIRQ pins. That's kind of a killer, because it means there's no way to route into the pseudo VIA2's interrupt flags. |
| 1 > |