Changing resolutions beyond the existing presets

[cannyboy]

I'm trying to change the resolutions (in os7 and os8) to work with my particular monitor - an old Dell 17" 1280 x 1024 VGA monitor - it's connected to the pi with a HDMI-to-VGA adaptor.

I've installed MacintoshPi on my R Pi 3B.

Ideally, I'd like to make os7 and os8 use exactly 1280 x 1024 pixels, so the image is crisp and sharp. (Alternatively, half resolution 640 x 512)

But I can't find a way to do this. I tried duplicating the /etc/macintoshpi/os7-600 and os8-600 folders and changing the resolutions in boot/config.txt like so:

framebuffer_width=1280
framebuffer_height=1024

That didn't work, I also tried changing the hdmi_group and hdmi_mode to the appropriate numbers. Still ends up fuzzy with small black bars at top and bottom. I'm not sure what the resolution being emulated is since the Monitors & Sound control panel doesn't work. (update: I found the right control panel in Apple Extras/Monitor extras)

Is there a way to get a sharp image, or have I hit a limitation with Basilisk?

----- UPDATE

I managed to get Mac OS 9 working at the right resolution (1280x1024) by changing the config.txt's framebuffer width and height and also changing a line in the macos9.cfg to screen win/1280/1024

However, when I try this with Mac OS 8, I get a torn screen effect https://ibb.co/4mtwsBZ

I'm going to experiment with the hdmi_group and hdmi_mode settings in config.txt

--- UPDATE

No luck with changing hdmi settings.. same tearing.

I noticed that the Quadra 650 tech specs don't seem to allow for 1280x1024 resolutions: https://support.apple.com/kb/sp232?locale=en_GB

... and neither do other Quadras, so I guess my hi-res journey is near an end.

My solution is to use the os8-480 preset, and add these lines to the macos8.cfg to make it crisp:

scale_integer true
scale_nearest true

Same for os7-480

[jaromaz]

Check the option:

overscan_scale=1 or overscan_scale=0

Check out my alternative configurations.