Due to a stupid accident by me, I acquired a 980m with a chunk knocked out of the core. Not wanted to scrap a perfectly good top end PCB for parts, I wanted to replace the core. You can see the gouge in the core to the left of the TFC918.01W writing near the left edge of the die.   First I had to get the dead core off:     With no sellers on ebay selling GM204 cores, my only option was to buy a full card off ebay. With no mobile cards under $500,I had to get a desktop card. And with this much effort involved to do the repair, of course I got a 980 instead of a 970.   Below is the dead 980 I got off ebay:     You can see for some reason someone removed a bunch of components between the core and PCI-E slot. I have no idea why anyone would do this. I tried the card and it was error 43. PCB bend seemed to be too little to kill the card, so those missing components had to be it.   GPUs can be dead because someone removed or installed a heatsink wrong and broke a corner of the core off, so buying cards for cores on ebay is a gamble. This core is not even scratched:     Preheating the card prior to high heat to pull the core:     And core pulled. It survived the pull:     Next is the 980 core on the left cleaned of solder. On the right is the original 980m core:     Next I need to reball the 980 core, and lastly put it on the card. I am waiting for the BGA stencil to arrive from China. It still has not cleared US customs:   https://tools.usps.com/go/TrackConfirmAction?tLabels=LS022957368CN   When that shows up expect the core to be on the card in 1-2 days.  
So some potential issues with this mod besides me physically messing up:   I believe that starting with Maxwell Nvidia started flashing core configuration onto the cores, like intel does with CPUID. I believe this because I found laser cuts on a GK104 for a 680m, but could not find any on two GM204 cores. In addition, Clyde figured out device IDs on the 680m and K5000m. They are set by resistor values on the PCB. The 980m has the same resistor configuration as the 680m for the lowest nibble of the Device ID (0x13D7), but all of the resistors are absent. Filling in these resistors does nothing. Resistors do exist for the 3 and D in the device ID. Flashing a 970m vBIOS on my 980m did not change the device ID or core configuration. If this data is not stored on the PCB through straps or the vBIOS, then it must be stored on the GPU core.   So I expect the card with the 980 core to report its device ID as 0x13D0. The first 12 bits pulled from the PCB, and last 4 from the core. 0x13D0 does not exist. I may possibly be able to add it to the .inf, or I may have to change the ID on the board. With the ID's 0 hardset by the core, I can only change the device ID to 0x13C0, matching that of a desktop 980.   An additional issue may be that the core may not fully enable. Clyde put a 680 core on a K5000m and never got it to unlock to 1536 CUDA cores. We never figured out why.   Lastly, there was very tough glue holding the 980m core on. When removing this glue I scraped some of the memory PCB traces. I checked with a multimeter and these traces are still intact, but if they are significantly damaged this can be problematic for memory stability. I think they are OK though, just exposed.   Due to Clyde's lack of success in getting his 680 core to fully unlock I am concerned I might not get 2048. If I don't at least I should still have a very good chip. Desktop chips are better binned than mobile chips (most 980s are over 80% ASIC quality, while most 980ms are below 70%). In addition this 980 is a Galax 980 Hall of Fame, which are supposedly binned out of the 980 chips. Having a 90%+ ASIC would be great to have. The mid 60s chips we get in the 980m suck tons of power.  
I want to give a special thanks to Mr. Fox. This card was originally his. He sent me one card to mod and one to repair. I repaired the broken one and broke the working one. The broken one is the one I've been modding.