https://arstechnica.com/gadgets/2019/07/the-snapdragon-855-is-getting-an-upgrade-to-the-snapdragon-855/

Today Qualcomm announced a mid-cycle upgrade for the Snapdragon 855, called the "Snapdragon 855+." As a mid-cycle upgrade, there aren't huge changes here. It's still an eight-core, 7nm SoC, but the CPU and GPU are a bit faster thanks to higher clock speeds.

First up: the CPU, which sees the 855's "Prime" core clock speed get bumped from 2.84GHz to 2.96GHz in the Plus version. Remember the 855's "Prime" core layout was a bit of a new thing for Qualcomm. It was typical to split the eight CPU cores up into two sets of four cores. The "Big" core set got a more-advanced core design and a higher clock rate for the heavy workloads, while a "little" set of cores had slower, more power-efficient cores for smaller workloads. The 855 took that bigger core set and pumped a single core up to a "Prime" core, so you had one Cortex A76-based core at 2.84GHz, three A76-based cores at 2.42GHz, and four 1.8GHz Cortex A55-based cores for the smaller cluster. The new "Prime" core clock speed means that only the single main core is faster.