[rescue] Mac IIfx compatible NuBus video card.

nate at portents.com nate at portents.com
Mon Oct 26 09:39:42 CDT 2009

> I recently lent a 15 pin Mac to VGA adapter to someone to use on a PPC Mac,
> and he had trouble with it. His Lenovo CRT monitor refused to work at all
> with it (the first time I had ever heard of such a problem) and an LCD
> monitor would work for a minute then a message from the monitor itself
> would come on the screen telling him to increase the resolution.
> In the end he found another CRT monitor which worked.

That's one of two issues.  Either a sync-on-green issue, or a resolution

Until the late-edition Quadra line, Mac video output was sync-on-green,
and not all LCD screens support it, since composite sync is much more
common now.

And regarding resolutions, back in the day before multisync monitors,
Apple used to have a monitor line that topped out with a 21" CRT that ran
at 1152x870, a 16" CRT that ran at 832x624, and a 13" CRT that ran at
640x480, all of which are 4:3 resolutions.  Other than 640x480, common PC
resolutions are different, like 800x600, 1024x768, and 1280x1024 (which is
a 5:4, not 4:3 resolution!)  I think it's only the Macs that do composite
sync that can display those PC resolutions as well - it all happened
around the time Apple stopped using Trinitron tubes exclusively and
started to make cheap, entry-level computers and peripherals.  Some
third-party Mac video cards had support for some of those PC resolutions
as well.

A good Mac DB-15 to VGA adapter will have DIP switches and/or dials to set
resolution capability for the monitor you're hooking up.

Viewsonic has a good track record for releasing LCDs that are compatible
with sync-on-green.  Whether a given LCD scaling engine can cope with the
"unusual" Mac resolutions of 832x624 and 1152x870 is another story.

- Nate

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