Talk:Problem with high pitch noises

Discussion of "Limit ACPI CPU power states"

• Stefan Baums: I raised this issue on the linux-kernel mailing list, and from there it was forwarded to the acpi-devel mailing list. See the discussion here and here. Results: The idle=halt kernel parameter disables ACPI C-state switching entirely (i.e., locks the processor in C1). It is preferable to pass to the ACPI processor component the option max_cstate=2, which only disables the problematic states C3 and C4. The only way to accomplish this that worked for me was to compile the ACPI processor component permanently into the kernel (CONFIG_ACPI_PROCESSOR=y) and then enable it by adding the parameter processor.max_cstate=2 to the boot command line (and of course removing idle=halt). Now the computer switches back and forth between C1 and C2, but avoids the noise-inducing C3 and C4, and frequency scaling works regardless. (X41)
• Simon Eggert: The processor.max_cstate=3 option worked for me on my T43p thanks.
• Adding options processor max_cstate=2 in /etc/modprobe.conf (or /etc/modprobe.conf.local on my SuSE 9.3 installation) prevents the CPU permanently from entering into C3 and higher states. (X40, R52)
• Thinker: On one T43, this worked even with processor.max_cstate=3. That is, C3 was silent and only C4 produced whining (at both HZ=100 and HZ=250).
• Thinker: These options affect power consumption when the CPU is idle. Here are the figures on one ThinkPad T43:
  • processor.max_cstate=4: 15160mW (default, noisy)
  • processor.max_cstate=3: 15770mW (660mW higher, silent)
  • processor.max_cstate=2: 16100mW (2940mW higher, silent)

on my T43p the noise definitely comes from the harddisk and can be heard both in Windows and Linux. Only at boot time, before the harddisk spins up, or when I manually spin down the harddisk with

# hdparm -y /dev/sda

the system is silent.