I have an HP DV6 6121tx with dual AMD+Intel graphics.

The AMD card has developed some issues, and Windows or Ubuntu don't work if they try to load it. Ubuntu throws out this error on boot:

http://i.imgur.com/txdej1k.jpg?1?6520

Now after a week of researching, adding this to grub gets rid of this error, and I'm able to run Linux off my Intel card with no errors:
"radeon.modeset=0 rd.driver.blacklist=radeon"

But the issue now is, that my AMD card still seems to be heating up. The palmrest area on my laptop gets pretty warm even with light use (running Chrome, nothing else). As a result, the battery life is half or less than half of what I'd expect it to be.

When my AMD card DID work properly, I still ran Ubuntu off the Intel card. But in that case, the radeon module obviously loaded without any problems, so I was able to use vgaswitcheroo. I simply switched the discrete card off from vgaswitcheroo, and my laptop ran with no abnormal heating or other issues.

Any insight on this issue? Is this simply too unique a situation for it to be solved?

PS: No, my BIOS has no option to switch off the discrete card.

Hello and welcome among the dissapointed linux users group of hybrid intel/ati video hardware.

Having said that, basically you have 2 options:

a) either disable completely amd card by installing acpi-call package so the kernel is instructed on each boot to switch it off. In such case you're left with Intel and MESA libs which lessens your 3d acceleration if you need it.

b) use an automatic script for vga switcheroo so you can boot up with intel and disable/enable AMD manually ---> look here

c) Digest that and switch to the newest fglrx driver for ubuntu, follow the instructions here

The third option may not be the purest one but fglrx-pxpress package especially developed for Ubuntu will give you control on switching between videocards one at a time. Once you do. you'll have to releoad lightdm service or just reboot your laptop to apply changes.

I have often read that "vga switcheroo" is only for when one has the non-proprietary AMD driver (the open source radeon module) installed and not the fglrx module; what if one has has neither the fglrx or radeon modules installed, but just the Intel? Can "vga switcheroo method" still be used to kill the AMD card?

Sure it can. By I meant switching the chip off/on not loading the driver.
It is Xorg that loads the correct driver to activate video output of one of the cards but still, if it loads integrated intel for instance, discrete ati can still be active as the whole thing works in muxless way. Get my point now?

Yeah, I understand the point that even with a driver for the dGPU loaded (whether fglrx/radeon), the discrete ati card could still be active taking power.

It is just the paragraph on the HybridGraphics wiki:

that has me a little confused, as I wanted to clarify the case for using switcheroo when neither opensource nor radeon modules are installed, but the card is left driverless. If the radeon and fglrx drivers are blacklisted, then vga switcheroo will not work? I think would need to reload the radeon module first with `modprobe radeon` then use switcheroo? (source: google)

Vgaswitcheroo will only work when no proprietary driver is in use. So, yes - it will work with radeon driver but not with fglrx and it will with intel as well.
I've assumed you chipset is a muxless one thus able to use one video output at a time, but it would be good to make sure it is.
To clarify your second point; It is not possible to run xorg in "driverless" mode unless you overwrite it with vesa settings. Even if it has no driver to load it will load vesa basic driver.
Getting back to your point. What exactly you are trying to achieve? Do you need 3d acceleration for games etc or you wanna stick to the opensource driver?

I have no fglrx installed on this clean build. Interesting you say it will work with intel aswell (even if radeon module is blacklisted??). The reason I ask is that is doesn't exist for me no matter what I do (modeset=1 etc). "/sys/kernel/debug" is mounted but nothing is there...This doesn't change if I unblacklist the radeon either.

My gut feeling would be that I would need a working radeon xorg (and need to unblacklist the radeon of course), to see vga switcheroo?

Any way I can check this for the AMD 8760M and Intel HD 4400?

I wasn't clear perhaps: I didn't mean completely "driverless"; I meant solely with the `i915` intel driver (no fglrx or radeon), for example a basic `xorg.conf` like

Section "Device"
Identifier "Intel Graphics"
Driver "intel"
EndSection

with a blacklist of the radeon modules in "/etc/modprobe.d/blockgfx.conf" means my Ubuntu runs on the i915 intel card alone.

I am trying to get rid of the AMD card altogether, to make my laptop as if it did not exist! hah. I have largely achieved this by blacklisting the radeon module and an intel only device config in xorg.conf, but unfortunately, as you pointed out the AMD dGPU is still eating up power! So I'd like someway to turn power it down altogether...

The radeon driver does not support my card yet, and my experience with the fglrx driver was not good, hence I just want to get rid of it and go back to intel, but not sure I can power it down, without a working radeon config or without fglrx pxpress...

Yeah, I guess it is possible even if I have not tried myself. Summing up - you don't want fglrx driver and radeon doesn't support your hardware yet so intel is enough for you. (Mesa provides basic 3d acceleration and some extra PPA with bleeding-edge libs do exist, so it is not that bad after all )
I would go for acpi_call if I were you. There is a section about it in the ubuntu wiki I've pasted for you before. Give it a try.