Along with the graphics driver GeForce 355.98 WHQLNVIDIA announced its GeForce GTX 980 for the laptop, the desktop GPU for laptops which is around 35% faster than GeForce GTX 980m. So you should not be confused with the GTX 980M, certainly a name which is very unwise to rise mistakes when it was expected to be called GeForce GTX 990M.

NVIDIA announces GeForce GTX 980 for notebooks 

NVIDIA-GeForce-GTX-980_Laptop_Overclock

Thus we have the same Maxwell Graphics core (GM204) with 2048 CUDA Cores, 128 TMUs and 64 ROPs to a base frequency 1126 MHz coupled with 4/8 GB of GDDR5 memory @ 7000 MHz with a memory interface of 256 bits, for we have essentially the same GPU desktop unless move with a TDP between 150 and 165W (165W vs. desktop). The reason being operated at 150W is that it will use the turbo frequency when needed, it will boost to the higher clocks, the maximum frequency is lower than the desktop alone.

Regarding its performance, it will be 35 percent faster than the GeForce GTX 980M and 10-15 percent slower than SLI of two GeForce GTX 970M. The laptop manufacturers will have to equip this GPU with a portable cooling system.

NVIDIA-GeForce-GTX-980_Laptop_GPU

GeForce GTX 980M GeForce GTX 970M GeForce GTX 980 (Desktop) GeForce GTX 980 (Notebook)
Process 28 nm 28 nm 28 nm 28 nm
Architecture Maxwell (GM204) Maxwell (GM204) Maxwell (GM204) Maxwell (GM204)
ALUs 1536 1280 2048 2048
Core clock 1038 MHz + Boost 924 MHz + Boost 1126 MHz + Boost 1126 MHz + Boost
Memory interface 256 Bit (GDDR5) 192 Bit (GDDR5) 256 Bit (GDDR5) 256 Bit (GDDR5)
VRAM capacity 4/8 GB 3/6 GB 4 GB 4/8 GB
Memory clock (eff.) 1250 MHz (5000 MHz) 1250 MHz (5000 MHz) 1750 MHz (7000 MHz) 1750 MHz (7000 MHz)
TDP ~100 W (?) ~80 W (?) 165 W <165 W

The first manufacturers to bring laptops with GeForce GTX 980 will be MSI (GT72 and GT80) Aeorus / Gigabyte (X7 DT), Asus (GX700VO) and Clevo  (P870DM / P775DM). All laptops will be equipped with software to overclock.

NVIDIA-GeForce-GTX-980_Laptop_Overclock