While trying out new ideas for fanxdell 2, I experimented with using the 30a3 / 31a3 codes in a modified fanxdell to enable and disable BIOS fan control when fanxdell started and exited, as described here:
http://unix.stackexchange.com/questions/63220/ubuntu-12-10-fan-overspeeding
However, this disabled more than the BIOS fan speed control on my Dell C840. Opening and closing several windows while the BIOS control was turned off with 30a3 saw the system running much slower than usual. I can only presume it turned off CPU speed control too, leaving the CPU in power saving idle mode. Issuing 31a3 returned normal operation, although the fan which was left running by the exiting fanxdell daemon was turned off, in line with BIOS temperature settings. Running sudo fanxdell -a with a regular fanxdell turned fan control back on again. So it looks like it does affect BIOS fan control, but unless you were going to programmatically deal with all the other items controlled automatically by the BIOS, these codes are of little practical use. So, although it looked an interesting concept to include in fanxdell 2, it has been given the boot!
http://unix.stackexchange.com/questions/63220/ubuntu-12-10-fan-overspeeding
However, this disabled more than the BIOS fan speed control on my Dell C840. Opening and closing several windows while the BIOS control was turned off with 30a3 saw the system running much slower than usual. I can only presume it turned off CPU speed control too, leaving the CPU in power saving idle mode. Issuing 31a3 returned normal operation, although the fan which was left running by the exiting fanxdell daemon was turned off, in line with BIOS temperature settings. Running sudo fanxdell -a with a regular fanxdell turned fan control back on again. So it looks like it does affect BIOS fan control, but unless you were going to programmatically deal with all the other items controlled automatically by the BIOS, these codes are of little practical use. So, although it looked an interesting concept to include in fanxdell 2, it has been given the boot!