Shortly after Apple issued 10.6.1, my 2009 iMac (2.93 GHz) began to randomly sleep, sometimes quite often, sometimes with hour-long intervals in between. The kernel began logging localhost kernel [0]: Previous Sleep Cause: - 101 after each incident.

None of the three Apple sources I contacted would precisely identity this error code. There was no reference to it that I could find on the internet. The standard reply I got was that errors logged with a negative sign are abnormal, which has been documented, and that although Apple's engineers were aware of it, the exact meaning was closed-source. I was told, however, that this indicated a "partial kernel-panic."�

In each case I told them I had no idea what they were or weren't allowed to say, and I didn't care -- I was just trying to fix the problem. I tried every possible method of booting Snow Leopard in both 32-bit and 64-bit modes, but couldn't solve the problem. Oddly, I wasn't able to reproduce the same random sleep with a re-install of 10.5.8.

Still under warranty until May of 2010, Apple made the repair by replacing the Main Logic Board of the iMac. It was part number 661-5133, the total repair cost would have been $1100, and it took the Apple Store in University Village just under one week. So if you're experiencing odd random sleep under 10.6 but not 10.5, it seems you may have a defective logic board, and it's probably worth a service call.

The new Macbook Unibody has about five ports. In my case, all of them are full all the time. Unless you buy a hub, why not use that defunct G5 for additional ports and devices? You may save some energy by not relying on a large number of external devices (keyboard, monitor, hard drives, etc.) or AC power. I was also tired of the issues with a USB powered Oxygen 8 keyboard from M-Audio. Using my G5, the VNC access is actually somewhat tolerable for light operations at reasonable resolutions. If you have your Mac configured with a SATA II card and an internal drive mounting system, you can have access to more drives at decent speeds.

These instructions cover setting up a FireWire 800 link, a MIDI Network Link, VNC access using Vine Server, which is much faster than ARD. Also, you can easily use your G5 as a bridge to connect to two-pin devices (most video-cameras). Latency is minimal and the data path is more than sufficient, if all other interfaces are disabled it is also somewhat secure. These instructions also go over the issues I have encountered, and specific Cocktail features that aid in VNC/file access.

Not so much a hint, but a suggestion which hopefully will help someone else. My iMac G5 (1.8 GHz, 2005 model) started having frequent kernel panics which I quickly realized was hardware related, as it persisted when booted from an external drive. When I opened the machine, I saw the dreaded bulging capacitors.

This was a known issue with a defect in the manufacturing of these capacitors, and Apple had a program to replace the motherboards when the capacitors failed. As I learned when I called the Apple rep, the program just ended in January and there was "nothing to be done." As I explained to the rep, I was being penalized for my machine lasting a bit longer than others, which made no sense. In fact, since there was no recall issued, I couldn't get my machine repaired before it failed, so Apple really had no choice in my opinion but to replace the defective motherboards. The rep agreed, and set up an appointment for my free replacement.

Hope this helps someone else who machine fails in the near future.

When I tried to boot my Mac Pro recently, it failed -- all I got was a black screen and a chime. I opened the case, and on the motherboard, I saw two LEDs were red: the cpuA and cpuB failure lights.

My warranty is over, but here are the steps I followed to get it working again:

1. Turn off your Mac and unplug the power cord.
2. Remove the CMOS battery on the motherboard (just above the graphic card).
3. Wait 10 seconds -- I'm not sure if this is necessary, but it worked for me.
4. Plug the power cord back into the Mac.
5. Press the power button. The Mac should boot normally and give you the startup chime, but you want your CMOS battery back.
6. Turn off the Mac, then unplug the power cord again.
7. Put the CMOS battery back in.

That's it; boot and enjoy!

[robg adds: I've never seen this on my Mac Pro, and I'm not sure if it's a sign of a failing CMOS battery, or something else. I'm publishing the hint because (a) it may help someone in the same situation, and (b) to see if anyone has any idea of what may be behind an apparent failure of both CPUs. Please comment if you have any thoughts.]

I've been swapping hard drives in my Mac Pro a lot lately, and they kept getting more and more difficult to pull out once they'd been soundly seated, to the point where I was in danger of bending the lip of the sled.

I was about to experiment with lubricating the things with a little graphite or similar, when I discovered that they slide out much more easily if you reach both hands inside the Mac and pull gently and evenly on the far edge of the drive itself.

Need an extra MacPro hard drive sled for swapping secondary hard drives? If you do not need to swap out your primary hard drive, take it off of the sled and carefully install it permanently into the first slot without the sled. First put some thick felt on top of the grey fan box. The hard drive is supported by the grey box and felt perfectly solid in this setup. Now you have a free hard drive sled to swap drives in the other three slots -- this is better than pay $29 plus shipping.

[robg adds: While I do have a Mac Pro, I'm not going to test this hint ... I don't swap drives often enough to merit a spare sled. Looking at the interior of the machine, though, it looks as though it would work fine -- though clearly it's not the recommended drive mounting method. Proceed at your own risk...]

When I upgraded the video card on my Dual 1.8ghz PowerMac G5, I started having many difficulties, including:

• Optical drive not recognized.
• Video card fails to power display.
• Hard drive(s) not recognized.

After several frustrating days, the solution was to reset the PMU on the motherboard. I suspect that on a newer G5, resetting the SMU would have the same effect. So, if you're out there having a hard time upgrading your G5, give it a shot!

[robg adds: I can't confirm this one -- if anyone has had a similar experience, please post.]

Apple's Intel Mac Mini has only one display connection, the DVI interface. In case someone has chosen a wrong display resolution for a connected display, it is very difficult to switch back to a usable resolution.

When (for example) using a Benq LCD connected via a VGA to DVI adaptor to the Mac Mini and changing the frequency from 60Hz to 75Hz, the Mini will always remember the chosen resolution, even if a PRAM reset or complete hardware reset is done. So the screen still stays black, as 75Hz can't be shown although the Displays System Preferences pane offers this frequency. It doesn't matter if you are connecting another display to the interface and afterwards changing the resolution; the Mini keeps on switching back to the former one if the misbehaving display is re-connected.

In order to switch back to a usable resolution, you will have to remote control the Mini from another Mac using screen sharing, Apple Remote Desktop, VNC, or Timbuktu. Even though the Mini's screen will be black, the remote Mac will show a usable image. While remote-controlling the Mini, you have to change the resolution within the Displays System Preferences panel. After changing the resolution remotely, the display should jump back to a usable resolution.

[robg adds: Apple provides a potentially easier solution to the black screen problem: use safe boot mode. Thanks to queue user fds for pointing this out.]

Some G4 Mirrored Drive Door (MDD) systems have cooling systems that run loudly as the CPUs get hot, especially the model affectionately known at the "Windtunnel" G4s. On those systems, enabling nap mode brings the normal operating temperature down remarkably well, thereby quieting the fans. This was covered in this older hint.

The method is basically to install the last version of Apple's C.H.U.D. tools that allows Nap Mode on those machines, which is version 3.5.2 [21MB download]. That version still works with Leopard, although notably it misreports cache sizes. However, the old command line utility, and therefore the derived AppleScripts, that people have relied on until now to enable nap mode have broken.

So here is an Applescript I wrote that will enable nap mode again, even under Leopard: Ideally the next version of C.H.U.D. Tools would bring Nap Mode back for these models which need it. Merciful Apple, why have you taken it away?

If you order a BTO Mac Pro with two internal hard drives, you may want to make a note of this. To make a long story short: Before firing up a new Mac Pro configured with two internal hard drives to run the Migration Assistant, turn it on in Target Disk Mode and rename the empty second hard drive to something other than Macintosh HD. Now, the explanation:

I was setting up a new Mac Pro for a user at one of my clients, and attempted to migrate her from her existing Power Mac G5. The new machine was configured with two internal hard drives, 500GB each. I attempted to migrate her data from the initial Setup Assistant, and everything went smoothly until we got to the actual "Transferring Information" screen -- no time estimate ever appeared in the progress bar, and the drives were not making sounds that would indicate they were being accessed.

I ended up rebooting the new machine via the power button and choosing not to migrate data when the Setup Assistant ran the next time. I made a dummy account and then ran Migration Assistant manually. I noticed that both internal drives on the Mac Pro were named Macintosh HD, and guessed that may have confused Migration Assistant. After I renamed the second drive, the copy proceeded without any problems.

To verify that the identically-named internal drives were indeed the problem, I stopped the migration, set the machine back to out-of-box state (except for the internal drives having identical names), and tried migrating the data from the initial Setup Assistant, and it worked flawlessly. I submitted a bug report to Apple about this, but thought I'd spread the word to possibly save someone else some time figuring this out before it gets fixed by a future version of Migration Assistant.