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Author ITXPlus: A ITX Sized Macintosh Plus Logicboard Reproduction (Read 75629 times)
Bolkonskij
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on: April 16, 2025, 14:52

max1zzz more or less casually announced a very exciting project - reverse engineering a Mac Plus logicboard.

The idea is to offer a modern reimplementation - you essentially get a Mac Plus in all its glory but *all* modern hardware. Read again - it's not re-purposing original chips, power supplies  or else. From what I understand, it'll be a fully modern parts replacement. That's quite an achievement if he ever manages to release it.

Quote from: max1zzz
ITXPlus is a Mini-ITX sized Macintosh Plus logicboard clone that can be be assembled to a working state with no original parts and is intended for new build systems in modern cases

ITXPlus features a onboard VGA output using GuruThree's Pico based video converter, power from standard 24pin ATX power supply, a onboard 50pin internal scsi header and 4MB of solderd RAM

ITXPlus also makes used of DosFox's discreet replacement for the Sony Sound IC and my implementation of his SCHWIM IWM bypass in a PLD as well as pgreenland / quortan's ATTiny based RTC replacement and Porchy / Hkz / Bolle's reverse engineerings of the Macintosh Plus PAL's

As it is designed to use a SCHWIM based IWM bypass it will not support floppy drives out of the box however a expansion heder is provided with all the signals required to connect a real IWM should you want to do this

With execption of the 68000, connectors and a few other little bits the board is fully surface mount, I almost went with a surface mount 68000 too but was convinced otherwise as it means the nice gold capped ceramic 68000's can be used.

The board will look something roughly like this.

Finally to answer the inevitible question: Why base it on the Plus? why not the IIci? or the SE/30? I chose to base it on the plus simply because it can be built with no original parts, this is intended to be a project build not the fastest possible mac out there.

If this gets released, it'll be the first no-original-parts classic Mac. Exciting!

Would you guys be interested in getting one and building your own system?

Jatoba
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Reply #1 on: April 17, 2025, 12:23

I wish this was based on the MDD, G4 XServe and other highest-end Mac OS hardware, but... oh well. :( They must be more complex to do?

With that said...:

Quote from: Bolkonskij
Would you guys be interested in getting one and building your own system?

Definitely! Above all, this is one MAJOR step towards TRUE ownership of Mac hardware that is capable of actually booting Mac OS proper in a more future-proof way, assuming FULL schematics are also made available with the board etc..

I'm assuming the CPU is not an FPGA, though, but a true 68000 processor, right? (Can we still source those somewhere?)

It'd have been interesting to keep the CPU removable with a "slot", but from what I understood, that would prevent real 68000s from fitting? Not sure.

I hope there's more of this in the future, but with a focus on G4 hardware. Real G4s (7448) are still produced today by NXP, last I checked in 2021. A Tsunami-architecture, 4 CPU Mac, just like some of the clones offered, would be beyond awesome, as well!

I tried searching for later Mac schematics before, but never succeeded. More on this here.

And always remember...:

http://revontulet.org/2025/04/17/638e724259df4cc28b16e648eb169688.png
Bolkonskij
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Reply #2 on: April 23, 2025, 07:11

Quote from: max1zzz
Boards have been sent off to JLC, hopefully I should have them in hand by the end of next week

Things are moving quickly. There'll probably be a few iterations of the board to iron out problems I suppose, but maybe later this year we'll have a known-to-work Macintosh board that isn't from Apple and uses no original parts. Exciting :-)
Last Edit: April 23, 2025, 08:08 by Bolkonskij
Knezzen
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Reply #3 on: April 23, 2025, 08:31

Wow! Give me one! :D
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