I’m shocked at how cheap this 4-core, 8-thread processor can be acquired.
Drive requirements have increased, and who needs the DVD drive? I’m triple-stuffing this iMac with three SSD drives and buying a slot-load enclosure (USB 2.0) for the old superdrive for external compatibility.
You are probably here to find out how to nvflash the HP K610M with the K610M_.rom.
Since you are going to upgrade your iMac’s video card, you have a lot of disassembly to do. Here are some quality videos to help you along the way.
It’s important to get all upgrades out of the way prior to completing the video card upgrade and nvflash. you may want to test things work prior to actually installing the new video card. Word of caution: you can’t see your screen once you install a non-Mac flashed card into the slot (I know that sounds insane, but you are expecting the video card to fail upon first boot and NOT work until being flashed remotely using SSH). So if you are like me and want to install new SSDs, new (larger) RAM modules, and an upgraded wifi card, you may want to try those things before you completely disassemble the computer. Making sure stuff works is an important step to logging into the soon to be headless iMac remotely. If this scares you then this upgrade is probably not right for you. I can’t stress enough, thinking “I’ll just throw all of these components in at once” is a terrible idea, if any of the components are bad or improperly installed, troubleshooting becomes a nightmare, you have to disconnect all the drives away to nvflash the card
Once you have this easier stuff in place and tested with the working slower CPU and Video card you can remove the motherboard and heat syncs from the main chassis (large aluminum back). Here are a few tips, in the top right corner (the heat sync for the video card) there is a fat head torx screw built specifically for that spot, all the other screw heads will be too small for the opening.

The six mainboard screws have about a quarter inch of thread at the bottom on all of the screws. One screw stands out as longer than the others, it fits a specific anchor point holding both the main board and processor heat sync neck assembly to the chassis (aluminum back).

When taking the motherboard out of the chassis, you don’t need to undo the small torx screws anchoring the heat sync assembly neck to the motherboard, if you do, the assembly kind of flops around and could potentially damage the under side of the board as you remove it. Just leave the processor heat sync attached to the motherboard and detach it once you have everything out of the chassis.
The mounting holes on the replacement video card are threaded, but the setup for the card attachment to the heat sync is actually reversed, requiring they (the screw holes) needing to get drilled out to match up with the mounting system Macintosh has in place.
cd /lib/live/mount/persistence/flash
Execute the following command from the directory containing QUADRO and nvflash_linux
./nvflash_linux –save ~k610mbak.rom
^ This will backup the current from the card in case you have to get back to it in the root user directory.
Next, wipe out built in protection on the card with:
./nvflash_linux –protectoff
Finally, Flash the card with the updated mac version ROM.
./nvflash_linux -6 Quadro/K610M_EG2.rom
Please read the updated commands carefully to understand what they are trying to do prior to executing, don’t just blindly execute commands you find online.