You got surprisingly close to GloFo's own density claims. They claim a 60% density increase, which is in one dimension. When you account for two dimensions, it'a 0.6x0.6=0.36.
So 7nm is 0.36x of 14nm in size.
And what you said about two nodes worth of density improvement is, well, exactly what it is. GloFo skipped 10nm to focus on 7nm, and their 7nm is competitive with other 7nm solutions. So they effectively jumped two nodes.
The key here is the choice of track count will determine the actual shrink.
14LPP - CPP = 78nm MMP = 64nm. CPP X MMP = 78 x 64 = 4992
7LP - CPP = 56nm MMP = 40nm . CPP x MMP = 56 x 40 = 2240.
So in terms of CPP x MMP the shrink is 2240/4992 = 0.45 . 55%. But when you bring in track count which determines the actual cell size the shrink can go upto 70%. 7SoC is enough to provide perf required for servers.
14LPP 9T to 7SoC 6T = 70% shrink
14LPP 7.5T to 7SoC 6T = 65% shrink
14LPP 9T to 7HPC 9T = 55% shrink.
7SoC 6T is aimed at a real sweet spot of power, perf and maximum density. AMD needs 7HPC only for Zen 2 desktop. I think servers and notebooks are better served by 7SoC.
Likely it won't need. The graph itself says that 7LP SoC have 30% more Fmax than 14LPP. That gives Ryzen a 5.2Ghz clock, at 80% of the power. It just couldn't be better.
http://btbmarketing.com/iedm/docs/29-5 Narasimha_Fig 2.jpg
imo the graph plots the most efficient regions on the freq/power curve for the respective processes. It does not cover the entire freq range upto fmax.
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