[Tuna-Fish]

Not at GDDR speeds.

GPUs use special DRAM that has much higher bandwidth than the DRAM that's used with CPUs. The main reason they can achieve this higher bandwidth at low cost is that the connection between the GPU and the DRAM chip is point-to-point, very short, and very clean. Today, even clamshell memory configuration is not supported by plugging two memory chips into the same bus, it's supported by having the interface in the GDDR chips internally split into two halves, and each chip can either serve requests using both halves at the same time, or using only one half over twice the time.

You are definitely not passing that link through some kind of daughterboard connector, or a flex cable.