The block diagram helped! Great summary. Did some additional readings as I forgot all about PCH and came across south bridge / north bridge which were familia

The block diagram helped! Great summary. Did some additional readings as I forgot all about PCH and came across south bridge / north bridge which were familiar sounding. As I understand, please correct me, summarizing parts what you wrote. So 16 lanes for GPU and the 4 (usually to PCH), which can be thought of as an extension? I'm not sure the right term but I guess this provides bus sharing through some mechanism so it does not affect the GPU lanes.