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How to change my display adapter to a standard VGA mode?

My Mac Mini Display Detection Dilemma

  • I've made the switch to a Mac Mini, and unfortunately it seems to be detecting my monitor capabilities incorrectly; how can I override this autodetection, or otherwise get around the problem? I'm using a (relatively new) Digimate L-1705 17" TFT monitor connected with the DVI-VGA adapter. The maximum refresh rate of the monitor is 75kHz, yet when the mini boots, the grey screen appears OK - but when it changes to the normal desktop screen my monitor reports a "signal out of range" error. I think that the mini thinks that the monitor can achieve a higher refresh rate than it really can, and is using this by default. How can I stop it doing this? I know that the computer works, as I carted it across town to my brother - using an old 14" CRT! This enabled me to register the Apple wireless keyboard and mouse, and set up a user profile. Whilst there, I set the display preferences to a setting that I knew worked with my monitor. Upon getting home and connecting the monitor, I got the same out of range message. Thus far, I've been on the telephone to Apple Tech Support for over 1h, and they've been able to come up with anything more useful than their presumably standard "reset PRAM, reset PMU, boot from CD, boot into safe mode" spiel - all of which I'd already tried, and none of which worked. Their other suggestion was to take it to an Apple store - but unfortunately this will require me to catch a 100GBP flight off the little rock on which I live. Hmph. Carrying the mini across town is OK, if there's something that I can do when connected to another monitor - but it's not feasible to carry my monitor across town as well. I don't have any other display unit (monitor, compatible TV, etc.) on hand which can be used. I can get into the Open Firmware (command option O F) and have had a poke around... is there anything in there (or accessible from there) which I can change to set the default screenmode? I can see the HD, but have no idea how to find/edit/remove files from the OF command line. I can also get into the single user mode (command S) but unfortunately once I'm in there I can't do anything, as the Apple wireless keyboard is not detected. Great! I'll happily buy/borrow a USB keyboard if necessary (my PC one is - typically enough - PS/2). There are http://docs.info.apple.com/article.html?artnum=301345 on the Apple support site, but unfortunately this doesn't work in my situation - safe mode goes out of range, and I can't type anything in single-user command line mode! http://discussions.info.apple.com/[email protected]@.68a7c773, again on the Apple suport site, appears to be my exact problem, but I don't have the option of using a compatible CRT screen and my TFT at the same time. I've also found a bunch of useful information on http://episteme.arstechnica.com/eve/ubb.x/a/tpc/f/8300945231/m/679008139631 but none of it has helped with this problem. I've posted my question there, too - but have had no joy yet. I appreciate that I've typed an awful lot so far - apologies! - but when it comes to things like this, I know that it's best to explain the minutiae of what's wrong and what has been tried... Hopefully there's someone here who knows everything there is to know about the underlying Mac architecture, workarounds, etc. - please?! (I've currently got every possible extremity crossed on the off chance that it helps...) Many thanks in advance! On preview: Hehe - "Extended explanation"... yup!

  • Answer:

    Uh... "they've been able to" == "they've been unable to" :-) One thought - would setting the display mode to a compatible one (using my brother's CRT monitor) and then protecting the display preferences file from being changed/deleted work? Would this cause a boot error? Does MacOS hold different display preferences for the different monitors that it detects? I'm (normally) a pretty tech-savvy bloke, and this is really beginning to get me down!

Chunder at Ask.Metafilter.Com Visit the source

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Keep the monitor turned off (at the wall) until the Mac has finished booting.

cillit bang

Tried that one - still comes up with an out of range signal. I even tried resetting the PMU, then booting, then plugging the monitor (and adapter) in after enough time has passed for it to boot fully... same result. Curses.

Chunder

Is there something you can do with the monitor's frequency setup? That is, adjust the monitor to a lower frequency than it is on now and then when you boot up the mac, it may autosense this new setting. Sorry I can't be more help, but my mini worked perfectly out of the box plugged into the dvi port on a sony display I bought for it.

birdherder

Nice quandry! My guess is this: that the boot picture is a lower monitor size (generic) until you get into the boot process...and it remember's your brother's machine setting. And why doesn't it recognize your keyboard under Single user? Bluetooth services haven't started....but it is very curious that they do seem to work under Open Firmware. Go to your brother's and set the monitor to 640x480. bring your flatscreen with you. With the mini on, detach the monitor and then see what happens. Of course, this is a strange one. There is a last ditch method; painful, but you seem to have some decent mac skill....you could set up a network at your brother's place, install VNC on both the mac and the PC. use the network to get ot the mac. Yes, It's a PITA. I'm sure there's a unix command, but I don't know it.

filmgeek

You may have to manually edit the com.apple.windowserver.plist file to the right resolution and refresh rate. A little more info can be found in http://forums.macosxhints.com/showthread.php?t=8235. The relevant section is the RefreshRate16.16 key for your monitor.

boaz

BTW, the RefreshRate16.16 is the refresh rate times 65536, so 75hz would correspond to a key of 4915200. Also, make sure the Width and Height keys conform to a supported resolution of the monitor.

boaz

boaz - sounds spot on! Exactly what I was after... now, any ideas how to edit a file from an OF command line? I've just walked around every shop (within walking distance) in town that's likely to sell computer bits (even a couple of stationery shops) and *nobody* has USB keyboards - everything is PS/2!! Nightmare! No single user command prompt for me just yet...

Chunder

A quote from the http://docs.info.apple.com/article.html?artnum=86651, which I'd not read before: "Note: Although you can use a wireless keyboard to start up in Single-User mode or in Safe Boot mode, they will not work once the computer is started up in these modes. To continue in Single-User mode or in Safe Boot mode, use a wired keyboard and mouse." - great. So much for the Mac being ideal for newbies - methinks Apple have tried to be too clever, and have forgotten how to do the simple basic stuff...

Chunder

Sadly, you can only edit a few very low-level settings in OF, none of which involve files on-disk, so no dice there. I would suggest carting it back over to your brother's house again, and bringing your LCD too for testing purposes. If you have the developer tools installed, you'll have a program called Property List Editor in /Developer/Applications/Utilities that will help with editing the file (though I think, since it's an admin file, you'll have to Save As... to a different directory and then copy it over in the Finder). There will be one DisplaySet for each monitor that you start it up with, so it might take a bit of trial-and-error to edit the right monitor entry.

boaz

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