Take the TR4 socket (threadripper) put half of the silicon's Ryzen 7 1700 on one side, and put on the other half the crappiest Vega GPU, integrate it to directly communicate with the CPU, thus eliminating the PCI bridge, hook it up to the quad channel DDR4 witch i know it does a half ass job regarding video processing bandwith compare to GDDR5 (maybe even stick on some sticks of HBM2 of 4 GB on that silicone, come on AMD, you can do it!) And sell it as an integrated APU at about 600-700 bucks? I mean... they can just mash that **** into a mini itx motherboard with no PCIe slot, but a m2 slot at least and make the ultimate xbox x (scorpio) killer. Why doesn't AMD do this? Is it because of the limitation of technology? I bet they can mash a ryzen 7 and a budget friendly vega into a socket like the TR4, i mean look at the size of it!
Because silicone is a rubbery substance for one. Secondly, directly connecting two rather large chips using a silicon interposer or EMIB and integrating HBM or HMC would likely cost over $6,000 not $600 like Knights Landing or Volta V100 do. Also, GPUs and CPUs arent on the same process node, and there would be packaging and thermal issues as well. Its not that it cant be done. Itd just be a lot more expensive than a CPU with a PCI-e GPU.