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Big Mac · Apr 29, 2010, 10:21 PM

Question: Is a PRAM reset accomplished by resetting the SMU on my G5? I ask because I'm wondering if a PRAM reset could restore lacking resolution options to my display.

Background: I just got my PC flashed NVidia 6800 card in my G5, and it works fine except for the fact that Displays doesn't show the native resolution of my LCD. I tried DisplayConfig X, and it sensed the proper resolution of my display, but after I installed it and restarted my G5 logged in normally (I could hear my Google notifier) but my display was just blue with nothing else, indicating that DisplayConfix X botched something. I'm finally back after doing a clean install of OS X (tried an Archive and Install but it got hung up at "about a minute"). I also had to dedicate a brand new 1TB drive my G5 just for the reinstall - oh well. Now I'm trying to figure out if there's any other safe option to try to restore the proper resolution of my display. (At least it beats a pink lined and dotted display that I had before.)

Btw, here's a funny anecdote: I haven't done a PRAM reset since my LC when it was ailing. At first it seemed to help but then I got a nice old bomb dialog, and I've never had to do a PRAM reset since. The experience left a bad taste in my mouth, even though I know it wasn't the fault of the reset. . .

reader50 · Apr 29, 2010, 11:37 PM

OS X doesn't seem to store display resolutions in PRAM any more. Instead, try here:

MacHD/Library/Preferences/com.apple.windowserver.plist

The display sets within this file define the monitor resolutions.

Big Mac · Apr 30, 2010, 12:33 AM

Thank you, reader. I think at this point I'm a bit too chicken to try force the resolution issue again. If I could force the higher resolution to show up in the display pane I could at least press esc to cancel the change if it didn't work out.

I don't see why this 6800GT is topping out at 1368x768 when my display is 2048x1152, but I guess I can't expect much more out of a flashed card I got off eBay for $47.

reader50 · 03:42 AM

Your flashed card may not have dual-link DVI ports. A single-link DVI port maxes out at 1920x1200. Your native resolution has 2.4% higher pixel count.

Try the other DVI port, only one may be dual-link. Alternatively, use a VGA connection if possible.

Big Mac · 01:22 AM

Oh!!!! Yeah, that must be what it is. I didn't realize that my 9800 XT was that special - didn't even know it was dual link. I thought that was only really important for dual displays. I shouldn't have second guessed the Display pane's wisdom. Cost me a lot of downtime having to do a fresh install. Well, at least I know what the deal is now.

reader50 rocks!

reader50 · Apr 30, 2010, 03:55 AM

2.4% above spec is a small margin. Some cards may have enough wiggle room to overload that far. I once tested a card rated at DVI max 1600x1200 with a 1920x1200 monitor. 20% overload. It worked in OS X outside of games, but was horribly unstable in OS 9. The VGA port was rated at 2048x1536, and ran the same monitor perfectly in all conditions.

If it is a bandwidth limit, then it depends on the specific components (and firmware) used on your cards. It might go a little past spec, or it may refuse to go past 1920 width. Or refuse 1920+ widths when outputting through a single-link DVI port. Do you have a 1920-wide monitor to test with?