What is the upgrade or equivalent to an old Phenom II X4 955 processor?
There is no equivalent as even the lowest end Ryzen, the R3 1200, is 63% faster.
If you mean equivalent in the product stack, the Phenom II X4 955 was the top of the line AM3 processor when it launched. The equivalent processor in the AM4 space is the Ryzen 7 1800X, although next month the Ryzen 7 2700X and possibly a 2800X will move into that space.
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