"ARM Holdings announced plans at TechCon last year to have a 20% market share in 2018"
That is only 1.5 years out. Now, notice that AMCC is up, while CAVM is down today (so far), it seems as though CAVM's strong competitive stance is already priced-in, AMCC's valuation may be rising based upon its initial steep discount, PAM4 could be more essential than first thought, X-Gene 3 is still seen as marginally better than Thunder-X 2, a win by either market leader will drive the eco-system for both players, or of course the prognostications of ARM Holdings could be only so much vaporware currently driving valuations.
"ThunderX2 is a 14nm FinFET design, and the company claims it will deliver 2 to 3 times the performance of ThunderX on select workloads with a higher performance to power ratio."
CAVM seems to be working with Samsung, as opposed to TSMC (16nm process vs 14nm) and CAVM vaporware seems to be keeping pace with AMCC vaporware.