February 8, 2006 8:05 AM PST

iMac Core Duo (#6): Video distortion: "Tearing" and other anomalies; Keyboard volume/eject keys fail; more

by CNET staff

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Video distortion: "Tearing" and other anomalies A number of readers are reporting an issue with distorted video from iMac Core Duo systems.

The problems are most noticeable when using Front Row to access video files and other media, and are generally described as "tearing" -- the appearance of horizontal lines or other distortions.

In most cases, the issue does not affect media played through QuickTime, the DVD Player or other applications -- only in Front Row and perhaps a few other areas of operation.

For many users experiencing this issue, the Apple Hardware Test shows only 128 MB of RAM installed when 256 is installed.

According to some posts on Apple's Discussion boards, users are able to resolve this issue by re-installing Mac OS X for Intel from a disc that contains the 8G1165 build rather than the 8G1171 build (two separate builds are currently circulating).

You can check which build of Mac OS X your system is using by accessing the "About this Mac" window (via the Apple icon pull-down menu in the upper left portion of your screen) then clicking the Mac OS X version number.

Apple Discussions poster "gualtie" writes:

"Today I've received the new system suite from Apple Ireland (I've told them about the second install DVD broken last friday: a very good and quick process from them!)

"The new system disk received was 8G1165, so I've reinstalled it and all tearing and flickering problems have been disappeared."

Since Apple is unlikely to supply a replacement Mac OS X installation disc for users experiencing this issue, your best bet is to find another user who has the 8G1165 Mac OS X 10.4.4 for Intel build and use their installation DVD on your afflicted system.

As another temporary fix, some users have reported that switching colors from millions to thousands (in the Display pane of System Preferences) resolves the issue.

The issue is likely to be resolved permanently with an upcoming maintenance release of Mac OS X 10.4.x.

Keyboard volume/eject keys fail Several readers have reported an issue where after waking from sleep, iMac Core Duos do not recognize input from the volume buttons nor from the eject key -- leading to some false reports that the eject key-based shortcuts do not work on these systems.

The simple solution is to disconnect and re-connect the keyboard.

MacFixIt reader Thorsten writes:

"I have found that after the machine has been sleeping, the volume buttons and the eject buttons on the keyboard are no longer functional. However, if I then unplug and re-plug the keyboard, their functionality is restored. Until next time the machine has slept."

Another reader, Paul, writes:

"Reporting the same issues: for no reason on my iMac Intel 20", the volume up/down, mute and eject shortcut keys sometimes stop to function. After a restart, it's OK again."

More problems with flash devices We continue to receive reports from users who have issues with USB-based Flash memory devices and their iMac Core Duos.

MacFixIt reader Mike writes:

"In my first experience with an Intel-based Mac, I couldn't load items from the 1G SanDisk Cruzer Compact Flash drive I use for loadsets. The drive would appear on the desk top, but when I went to transfer files, it would hang halfway through, requiring a power re-set to recover. Same with both a Mac- and PC-formatted drive."

It has yet to be determined whether or not this problem relates to a potential USB power draw issue with the Core Duo processor, documented in this eWeek article.

If you are having any USB-related issues, or any other problems with your iMac Core Duo, please let us know at late-breakers@macfixit.com.

Previous coverage:

Resources

"gualtie"

eWeek article

late-breakers@macfixit.com

iMac Core Duo (Early 2006)...