68kMLA Classic Interface
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| VIA Plus: a small debug board for 128K/512K/Plus | |
| Posted by: demik on 2025-03-11 06:35:31 Hello everyone, Posting this here, this is really niche. Built it while developing other stuff for early Macs It's a small debug board that plug in place of the VIA (or on top of if you can find the correct clip). It includes a 7 segment display which is useful for displaying the following informations: - /RESET status - OVERLAY status - RTC pulse (1 Hz) - Vertical refresh pulse (slowed down to 3.75 Hz) - Current sound volume level  Design is Open Source. Feel free to adapt it to others Macs or include it into something else like custom replica boards oldworld/EDA/VIA Plus at master · demik/oldworldDevelopment ressources for Old World Macintosh (68k and NuBus PPC) and a few related things… - demik/oldworld
github.com
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| Posted by: mdeverhart on 2025-03-11 07:34:32 That’s really cool, thanks for sharing! | |
| Posted by: David Cook on 2025-03-11 08:02:20 Fascinating. Clean build, too. Tell us more about the values it monitors. What kind of issues can it help catch? | |
Posted by: demik on 2025-03-11 09:22:12That’s really cool, thanks for sharing! Fascinating. Clean build, too. Thank you. It's a passive devices. Two examples that happened - tweaking ROMs or stuff plugged into the ROM slots. The display will display "o" because the overlay was kept active. Reason: damaged ROM socket: ROM not read, so overlay kept asserted - black screen (CRT) display, no visible vsync on the (7 segment) display: dead LAG Both issues could have been diagnosed with an oscilloscope, but somedays I'm too lazy to get the scope out Note that I'm using this with a board where most components are socketed, this is my lab board that is used to test components | |
Posted by: David Cook on 2025-03-11 11:58:28The display will display "o" because the overlay was kept active. Very clever. | |
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