I have an Asus Radeon HD 4850 1GB, made for HP. Because of a well-known problem with these cards being hot but silent, I updated the BIOS to this BIOS. This fixed the heat issue but makes the fan run loud. So I enabled DPM, which should have been enabled on my Debian 8.2 3.16 kernel automatically, and it clocks the card down now.

However, if you look at the link above, there are four clock states in the BIOS: one boot, one performance, one mid-range, and an ultra-low-power clock state. But on my running system I only ever see clock states 2 and 3, the mid-range and performance states. I never see clock state 1, which is the ultra-low-power clock state. And obviously, the boot state is only used on boot. But I would like to get it into low power mode if possible, so thanks in advance for any help.

I saw the different clock states but the dilemma seems to be how to change them.

I have a few ideas but I could be completely off:-
Some machines CPU supports frequency scaling.
Try running this command to see if it has a cpufreq sub-directory.

This will return something like .../ cache/ crash_notes microcode/ node0@ topology/ (or something similar)
If so it doesn't have a sub directory.

I'm not sure if changing the frequencies will stop the fan from being loud or not.
I've only tried this in Centos and in FC so I'm not sure if this will work for you.

This command will tell you if scaling frequencies are an option.
This cmd will show you all the frequencies:
There are speeds you can set using 'cpuspeed' or 'cpupower' but again; I only tried it in Centos and Fedora.

I talked with a member about this years ago and from my notes I remember him telling me that if you try any of those cmd's and it's on a system with a CPU that does not support frequency scaling the service will fail. He also warned me that messing around with the CPU frequencies can stop the system from dropping back to low power /mhz modes at low loads.
-::-Lurk before you leap. (do a little research)-::-

Aside from that the only other thing I can think of is look in the cpupower.service conf file and see if there are any instructions to change frequencies (if you haven't already)or see if there is a way to modify the performance governor.

***Warning: Some of the steps outlined below describe how to tweak fan speeds. Before doing this be sure to have a low CPU load.***
https://wiki.archlinux.org/index.php/fan_speed_control
https://wiki.archlinux.org/index.php...quency_scaling

http://superuser.com/questions/46288...m-the-terminal

You're talking about the CPU; I'm talking about the GPU. My CPU is doing nicely, with a silent fan, automatic frequency scaling, and temp readings of 23 to 25C at idle (room temperature ). The GPU is actually doing reasonably well now too; a case fan positioned well and the GPU fan help cool it and it's 36C with the screen off, 48C playing a game. It just gets a little noisier than I would like.

PS: I have also done quite a bit with CPU frequency scaling and governors in my time with Linux.

Sorry I was focused on CPU for some reason.

Glad to hear that the GPU is running a little more reasonable now.

Is it just one fan on the GPU or 2 fans?
I've seen some graphics cards with 2 fans.

This card only has one fan, and it's fairly whiny, so I screwed a case fan on the inside of the grate on the side of the case that's meant for cooling PCI-E cards. Being a case fan, it has more of a dull, low noise, so it's more tolerable to use that to help keep the GPU fan from running as much. So I have a total of four fans: CPU, case rear, GPU, and case side.

It sounds like you have pretty much done all that you can with that tower that you have.