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ITXPlus: A ITX Sized Macintosh Plus Logicboard Reproduction
Posted by: max1zzz on 2025-04-15 16:04:11 I haven't done project thread in a while as writing is not my favourite past time but people seem to enjoy them so here it goes 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 (I hope I haven't forgotten to mention anyone's elses work I have used....) 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: Though as you can see there is still most of the routeing work to do so things may get moved around a little 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. When finished the design will be fully open source and posted to my GitHub 🙂
Posted by: cheesestraws on 2025-04-15 16:18:05 I've been really looking forward to the first 'no original parts' board build. This is a milestone and a half. Well done.
Posted by: luRaichu on 2025-04-15 16:33:03 Next: A Macintosh Plus built without original parts. I'm sure they're still making b/w CRTs somewhere in China
Posted by: max1zzz on 2025-04-15 16:46:32 I've been really looking forward to the first 'no original parts' board build. This is a milestone and a half. Well done. Thanks 🙂 Though strictly speaking I think DosFox is the first one to do a "no original parts" build - he built a clone board based using my original Plus Reloaded board and most of the other bits mentioned above
Posted by: cheesestraws on 2025-04-15 17:08:52 Sorry, I meant 'design', as in actually a new board with new bits on.
Posted by: Gothikon on 2025-04-15 22:57:55 Fantastic!
Posted by: max1zzz on 2025-04-17 16:15:08 Getting there! Still quite a bit to do but it's finally at the point there are more red and green lines than white lines 🙂
Posted by: mattsoft on 2025-04-17 21:31:43 cool idea and cool project!
Posted by: max1zzz on 2025-04-19 05:58:08 MLB is done! Just need to draw up the riser with the keyboard / mouse / serial ports on it
Posted by: joshc on 2025-04-19 08:11:22 This is cool. I don’t need it but I want to build one… this seems like a great way to get a Plus without having another compact to find space for. A slim ITX case could be used. Although surface mount isn’t my favourite kind of soldering but I can understand why it was based on SMT. This would lend itself well to a kit where all the parts needed are supplied… 🤔
Posted by: max1zzz on 2025-04-19 08:53:58 It may actually be possible to build one of these with more TH parts, Probably not fully TH but there might just be enough space to squeeze in DIP parts for all the logic and PAL's and maybe the SCSI controller, ROM / VIA / SCC would have to stay as SMT parts though as there just isn't the space for the DIP packages (Though maybe TH PLCC sockets could be used.......) It's something I might look to do in the future as I was quite surprised a how much free space there actually is
Posted by: max1zzz on 2025-04-22 07:46:17 Boards have been sent off to JLC, hopefully I should have them in hand by the end of next week 🙂
Posted by: adespoton on 2025-04-22 16:23:10 Boards have been sent off to JLC, hopefully I should have them in hand by the end of next week 🙂 How large a run are you doing?
Posted by: max1zzz on 2025-04-23 00:42:54 At the moment just 5 to see if they work, I may do a larger run later though (It will also be open source so you will be able to make your own too 🙂 )
Posted by: max1zzz on 2025-04-28 09:30:51 PCB's are here!
Posted by: Big Ben on 2025-04-28 15:10:42 This is the call for testing and glory! ahem Looks great! Can’t wait to see it in action, nice work!
Posted by: max1zzz on 2025-04-28 15:39:17 This is the call for testing and glory! ahem That'll be tomorrows job 🙂 All the non programmables (and the ROM) are soldered down, will get all the PAL's programmed and installed tomorrow. Also still waiting for a pico to arrive as my spare one is AWOL
Posted by: max1zzz on 2025-04-29 16:47:18 It's late and I'm not doing a full write-up tonight, but I'll just leave these here (excuse the potato video, it's that or a massive file and I cba with trying to compress it right now) View attachment IMG_4320.MOV
Posted by: mg.man on 2025-04-29 16:54:28 Wow! You go walkabout for a few, err... yrs(!) and this sort of thing happens! Amazing! 😳
Posted by: Big Ben on 2025-04-29 22:43:55 It boots! 😲 Congrats!
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