The pending GeForce RTX 4080 will be available in two variants based on memory capacity, memory bus width, and perhaps core arrangement. 

MEGAsizeGPU has seen reference designs for the RTX 4080 with 12 GB of memory on a 10-layer PCB, as well as 16 GB of memory and a 12-layer PCB. Adding PCB layers improves the density of ASIC wires. The RTX 4090 is expected to be NVIDIA's flagship product, featuring 24 GB of RAM and a 14-layer PCB. The PCB designs for the 12 GB and 16 GB RTX 4080s are unique.

MEGAsizeGPU 
@Zed__Wang

4080 12G GD6X 10layer PCB aic reference design
4080 16G GD6X 12layer PCB aic
reference design
4090 24G GD6X 14layer PCB aic reference design

note：4080 12G has a completely different pcb design from 4080 16G

Update: The speculated 12 GB and 16 GB versions of the upcoming NVIDIA GeForce RTX 4080 will be released at the same time, says MEGAsizeGPU, which was the first to report that the RTX 4080 would come in two memory-based versions.

Update 2: According to leaked specifications, the 16 GB RTX 4080 is based on the same AD103 semiconductor, the second largest after the AD102; the 12 GB RTX 4080 is based on the smaller AD104 chip, which has a physically narrower memory interface. NVIDIA appears to be launching the RTX 40-series with at least three models: the RTX 4090 24 GB, the RTX 4080 16 GB, and the RTX 4080 12 GB. The top-tier part is the RTX 4090, which has the ASIC code "AD102-300-xx." It presumably has 16,384 shader cores, a boost frequency of up to 2.52 GHz, 24 GB of 21 Gbps GDDR6X memory, and 450 W of normal graphics power (TGP), which is "configurable" up to 600 W. The RTX 4080 16 GB is based on the AD103-300-xx" and features 9,728 CUDA cores, a boost frequency of 2.50 GHz, and 16 GB of GDDR6X memory with a smaller memory bus than the RTX 4090. This card is said to have a 340 W TGP that can be configured up to 516 W.

GeForce RTX 4080 Could arrive in 12GB and 16GB Variants (updated)