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Troubleshooting the Power Mac G5: noise issues

Troubleshooting the Power Mac G5: noise issues

General noise issues We've been receiving a significant number of confirmations and independent reports of noise with Power Mac G5 systems. However, there appear to be a number of different types of noise that users are experiencing:

  • A continual "chirping" noise that occurs when the Processor Performance setting in Energy Saver preferences is set to Highest. Changing this setting to Automatic or Reduced seems to avoid this particular noise.

  • A constant ticking or beeping noise whenever the computer is "idle" -- if processor-intensive tasks occur, the noise seems to disappear. (It's not yet clear to us if this is actually the same noise as the previous one, just described differently by different people.)

  • An overall humming of the machine that seems to be attributable to the power supply fans. Some users have taken to calling this a "fish tank hum" due to its similarity to the sounds produced by fish tank equipment. We mentioned yesterday that changing the Energy Saver settings to "Never" sleep seems to fix this problem for some people.

  • A "metallic screeching" or "static" that varies in frequency with processor load. Here at MacFixIt, we've experienced this issue on our own dual-2GHz G5 when resizing text clippings in the Finder. Reader Marc Jones points out that for him the "screech" is worse if he selects a QuickTime movie in the Finder or when using InDesign. At least in our case, installing Apple's CHUD tools and disabling the "Nap" feature completely eliminated this noise.

MacFixIt reader "Euge" has actually posted a sound file of various noises made by his dual-2GHz G5: "Begins with HUM-Buzz-Chirp; after 20s I disabled Nap to have only Hum-Buzz."

Reader Markus Altendorff has also posted a few excellent demo sound files, and provided a few informative comments:

    I can confirm the PSU noise problem - my machine beeps/chirps under any of the following conditions:
    a) Graphics card use, esp. with OpenGL
    b) Copying files over a network
    c) Opening a file in Quicktime player

    After installing the CHUD tools (Apple, Developer software), disabling "CPU Napping" (some sort of power-down mode during idle clock cycles) makes the chirping go away COMPLETELY and instantly.

    My guess (and backed by a friend of mine, former electronics pro and now IT...) is that (cheap) filter coils in the PSU start to vibrate, similar to loudspeaker coils, when the CPUs switch between high and low power use, which can happen very often at 2 GHz clock cycle. Since disabling CPU napping results in the CPUs consuming a fairly constant current, the vibrations stop (the magnetic fields in the coils remain constant).

    The bad thing about this is that the chirping also shows at the USB and Firewire ports, causing trouble when you try to use this computer in a recording studio - the thread at Apple Discussions contains quite a few complaints about how the G5 is barely usable for audio production because of this.

Several readers report that Apple replaced the power supply in their G5 as a result of noise issues. In some cases this solved the problem, but not in every case.

What makes these issues more than just annoying for some users is that some of the noises are transferred via USB and FireWire connections, and some are amplified by connected audio equipment -- reader Catherine Vibert reports that a "whining" noise is actually transmitted to the DIGI002 in Pro Tools via Firewire. These issues make affected G5 computers unusable for digital audio work.

Unfortunately, it's difficult for us to correlate noises with potential solutions because many people who have sent reports to MacFixIt have been vague about which noise their particular G5 is producing. There are clearly different problems and different solutions. If you send us email on this issue, please state which of the above "noises" your Power Mac G5 is producing and which, if any, technique reduces which noise.

Full-blown fans We've also received a number of additional reports of an issue where putting the G5 to sleep results in the fans revving up to full speed (which is startlingly loud if you've never heard it). Sometimes the situation can be resolved by waking the G5 up and then putting it back to sleep; however, sometimes the G5 will refuse to wake up, requiring a restart. We had this happen once to our G5 here at MacFixIt.

Entourage causing high CPU use and fans? In addition to the general issues with fans and other noises, some readers are finding that particular applications seem to immediately affect CPU use and fan speed. David Morganstein writes:

"I and another dual G5 user have the same experience when either opening an HTML email or displaying it in Preview Pane with Entourage X (10.1.5). The CPU usage revs up to 75% and the fans come on high. We suspect this is not an Apple or Panther problem but a Microsoft one. We experience this in either Panther 10.3 or 10.3.1."

We've seen similar reports from other users.

Is your Power Mac G5 powerfully noisy? Drop us an email at

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