My Mac Mini Display Detection Dilemma

May 28, 2005 4:08 AM

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 some instructions 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!
This discussion, 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 ars technica 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!

posted by Chunder to computers & internet (17 answers total)

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!
posted by Chunder at 4:15 AM on May 28, 2005

Keep the monitor turned off (at the wall) until the Mac has finished booting.
posted by cillit bang at 4:30 AM on May 28, 2005

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.
posted by Chunder at 4:53 AM on May 28, 2005

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.
posted by birdherder at 6:18 AM on May 28, 2005

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.
posted by filmgeek at 6:27 AM on May 28, 2005

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 this thread. The relevant section is the RefreshRate16.16 key for your monitor.
posted by boaz at 6:28 AM on May 28, 2005

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.
posted by boaz at 6:32 AM on May 28, 2005

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...
posted by Chunder at 9:53 AM on May 28, 2005

A quote from the Apple support website, 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...
posted by Chunder at 9:58 AM on May 28, 2005

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.
posted by boaz at 10:44 AM on May 28, 2005

No one sells a PS/2 to USB adaptor?
posted by birdsquared at 11:28 AM on May 28, 2005

did you walk around to he shops looking for a fixed-frequency VGA adaptor? These things force the box to deliver video at specific settings via hardware DIP switches. You did not specify if the video output chain is Box - DVI - adapter - VGA - Monitor but I surmise that's the case. I don't know if adding the FF adapter to the chain will have an effect, but if the chain above is correct, the new chain would go Box - DVI - adapter - FF adapter - VGA - Monitor.

beyond that, heading back to your brother's with the flatscreen and mini to fiddle around is probably your best best. Alternatively, if it's really impossible to move both items, see if your brother can bring over his monitor. You'll need to set a video resolution, swap cables, rinse, repeat.
posted by mwhybark at 4:16 PM on May 28, 2005

Also, this hint seems to suggest that holding down the shift key during startup will reset your monitor to default settings, which, given that it seems to be mis-detecting the default frequency, may or may not help in your case. But hey, worth a try before you start driving around.
posted by boaz at 4:37 PM on May 28, 2005

Actually, as soon as I posted that, I thought to myself, "Wait, isn't that how you boot into safe mode?", and the hint's so old that it might be from before safe boot mode was added. So, uh, scratch that.
posted by boaz at 4:44 PM on May 28, 2005

If you just bought the mini, you can telephone Apple for support. You get free telephone support for the first 90 days. if you're near an Apple Store, you could also bring it (and the monitor) into the genius bar for a consult.
posted by alms at 8:40 PM on May 28, 2005

flashgeek: but you seem to have some decent mac skill... LOL! This is my first ever Mac :-) We used to use LCII machines at school, but I was only in my early/mid teens (abot half my life ago!)... and everything about the system has changed since then! I was brought up on Amigas, which I suppose is why I'm comfortable hacking around with different things, and have a (perhaps vague) understanding of what things do and why.

birdsquared: Never thought of that - didn't even know that there was such a thing. I thought that USB keyboards needed some kind of ID chip in them so that the computer knows what they are... that will be my next attempt if I can't get a real USB keyboard.

mwhybark: The VGA monitor is connected using the Apple-provided DVI-VGA adapter, so the sequence is Mac mini -> DVI-VGA adapter -> TFT monitor. No different to anyone else using a VGA monitor with a mini...
Carrying the monitor to my brother's place, or his here, is not feasible - it's a fair old walk, and neither of us have ready access to a car ATM.

alms: Thanks for trying to help, but I can only assume that you skipped over paragraph 5 of my initial post? ;-)

boaz: I've got two more shops that may have USB keyboards to check; failing that, one of the shops is getting some stock in on Tuesday. I'm pretty optimistic that your suggestion will work - I'll let y'all know when I've been able to try it!
posted by Chunder at 2:13 AM on May 29, 2005

Ay caramba! This is ridiculous! I managed to find somewhere that sells USB keyboards, and pounced on one - a bog standard Kensington for 10 GBP.

I get home, plug it in, boot up holding down Cmd S, and up comes the single user prompt... but it doesn't recognise any input from the keyboard! WTF?!

Whilst buying the keyboard, I spied a PS/2 - USB converter (a small small in-out lump of plastic and metal; no cables like the one you linked to, birdsquared.
When connecting my PC PS/2 keyboard with this, I get a string of errors (relating to AppleUSBOHCI).

I think that I've bought a turkey :-(

Do the USB ports on anyone else's mini feel kind-of "loose" (i.e. the plug has freedom to wobble a bit)?
posted by Chunder at 7:55 AM on May 29, 2005