Victor Porton's Personal Weblog

A computer produces mosquito-like high tone noise when certain software is started. And it probably is not a cooler. I suspect that the mainboard itself produces the noise.

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The computer has the following components:

• mainboard ASRock PVM800/M/ASR (VIA PM800 chipset; mATX 800 MHz);
• CPU Intel Celeron 310D 2.13 GHz 256 Kb 533 Box;
• DDR 256Mb Samsung original;

On the computer is installed Linux 2.6.7 with custom compilation options and modules. (I normally do not launch any processor control modules.)

The problem is that when I start certain software, the computer immediately begins to produce irritating mosquito-like high tone noise (in addition to the normal coolers' noise). As soon as I stop this software the mosquito noise ceases.

For example the noise appears with certain X11 screensavers when I configure 1024x768 x 16 bit framebuffer (using VIA's framebuffer driver version 20050726), then start X11 (XFree86 Version 4.3.0.1; fbdev) and then start certain screen savers. (The noise appears while these screensavers are working.)

The noise appears in both cases when the screensavers are running in the root window and when they are running in a normal window. One can start these screensavers in a window (to start to produce the noise) with the following commands (from xscreensaver package):

/usr/lib/xscreensaver/ant
or
/usr/lib/xscreensaver/bubbles

My first thought was that the mainboard automatically detects increased CPU load and increases CPU cooler speed what produces the noise. But no, I have checked that CPU load while running these screensavers in a window is low, so it should be not CPU cooler, yet the sound appears.

My second thought was that is is the monitor. But the noise appears even when the monitor is turned off. It also appears when the above mentioned programs draw invisibly in the background, below other windows, so not influencing the monitor. So the thing which produces the noise is not the monitor nor it is the monitor cable.

Only two variants are left: either this is one of the two coolers (on the CPU despite of its low load) or in the power supply (There are no other coolers in this system.), either this is the mainboard itself.

Then I have thought that the thing which noises it the on-board video chip (S3 Unichrome), but some noise seem to appear (yet little tested) also when running certain sound processing software instead of the above mentioned graphics software.

What I have left to thought that it is the mainboard itself (a mainboard bus) what produces the noise. I suspect that the electricity on the board makes noise as the wires may possibly influence each other with magnetic field and so vibrate.

Linux 2.6.7 which is installed there does not have fan (nor thermal) drivers for this mainboard (PVM800). So I now can't tell for sure that it is not the coolers. I hope that after the next Linux kernel update I will have fan (cooler) drivers and will be able to check for sure whether fan speed increases or not.

In the meantime I suggest the mainboard producer (ASRock Inc.) to check their mainboards and ensure to remove the noise as it is very irritating.

Tags: ASRock, mainboards.