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Reverse Engineering the Macintosh LC III Logicboard

max1zzz

Well-known member
Copper areas are now done!
9-9-21.JPG
It doesn't look that much different, but it took ages to draw all those areas....

Next thing to do is the inner layers which are always fun!

It;s amazing quite how much more apple packed onto that board compared with the LC, the LC has about 850 via's on the board whereas the LC III has over 1600!
 

max1zzz

Well-known member
Annnnnd, I think we are done!
14-9-21.JPG
That took way longer than I expected, these boards are really densely packed!

Time to send it to JLC :)
 

claanu

Member
Nicely done. The LC III was my first Mac. I've also somehow acquired oodles of orphaned LC III boards over the last year, so this project might be very personally relevant soon.
 

ronan

Well-known member
Naive question : are the Macintosh LC III chips easy to source ? I suppose that adb chips for instance are harder because apple specific but what about the others ?
 

max1zzz

Well-known member
Naive question : are the Macintosh LC III chips easy to source ? I suppose that adb chips for instance are harder because apple specific but what about the others ?
Unfortunately not, the board uses a custom memory / system controller (The big chip in the centre of the board), a custom clock chip, custom DAC's for both video and sound and the custom ADB / rtc chip (Egret)

The egret is in theory just a motorola microcontroller and I believe the code has been dumped form it, but sourcing that long obsolete chip or the equipment to program it is damn near impossible, I belive code compatible (but not pin compatible) chips are still made but as of yet no one has made a replacement.

There is also a little 8 pin custom (or custom marked) chip that handles the switching between battery and mains power for the Egret and a couple of reset lines, there is a chip that is readily available from china in the same package, with a simmiler part number (that also looks like a apple part number) but until I get my order of those I don't know for sure if that is the right part (the part is marked 0120, the part form china is sold as 343S0120)

Basically a doner board is needed to build one of these, thay are mainly intended for saveing battery damaged boards :)
 

demik

Well-known member
The egret is in theory just a motorola microcontroller and I believe the code has been dumped form it, but sourcing that long obsolete chip or the equipment to program it is damn near impossible, I belive code compatible (but not pin compatible) chips are still made but as of yet no one has made a replacement.

IIRC, only the SE one (PIC based) has been dumped using a microscope, and one version of CUDA was dumped via a trick as well.
Unfortunately, nobody managed to get either one running as far as I know.

Anyway, nice work again ! I'm crossing finger for the first boot
 

olePigeon

Well-known member
Has anyone considered a "remix" board? Like taking a Q605 and changing its dimensions and port orientation so it'll fit into, say, an SE/30 or Macintosh Classic?
 
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