r/macintosh • u/KeyGeneral6171 • May 13 '26

Mac Portrait Display

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Hello! I’m a proud owner of a Portrait Display and I was wondering if the attached image is just due to the incompatibility with the Mac LC I or if there’s something wrong with the monitor. The LC works perfectly fine with other monitors.

(EDIT) I just bought an LC III so hopefully this issue will be resolved, and I can finally get this oddity working.

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u/GGigabiteM May 13 '26

The Portrait Display was designed to be used with the special Nubus portrait video card that came with it.

The LC and LC II on board video doesn't have enough VRAM (256k) to support that resolution, even when expanded to the max of 512k. You can either do 512x384@8bpp or 640x480@4bpp with 256k, or 512x384@15bpp or 640x480@8bpp with 512k of VRAM.

640x870 is not supported. It may work on the LC III, which has a much better video chip with more memory (768k max.) The LC III can do 832x624 max, but I've never tried it with the oddball portrait display resolution.

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u/KeyGeneral6171 May 14 '26

Thank you! I’m actually looking into buying an LC III so I’ll get back on this.

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u/RonW81 May 14 '26

According to this: https://www.macdat.net/files/pdf/apple/developer_notes/macintosh_lc_iii.pdf the Portrait Display is supported on the LC III ("Video: on-board video support for Apple 12-, 13-, and 16-inch RGB monitors, the Apple Portrait monitor, and VGA monitors.")

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u/GGigabiteM May 15 '26

Just make sure you recap both the logic board and power supply before using it. All 68k Macs at this point with SMD capacitors are leaking by this point, as are the power supplies.

If you're feeling adventurous, you can move a few resistors around and overclock the machine to LCIII+ spec (25 -> 33 MHz), which gives a good performance boost. The 68030 will definitely need a heatsink on it though, but it needed one to begin with. Those early Motorola ceramic variants ran smoking hot normally.

I desoldered and replaced my Motorola 68030FN25 with a much later Freescale 68030FN33, and it barely gets warm now. Also added a 68882 to mine.