Are they 2 variants of 5820K? What does Rev.R2 means?

David19800

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Feb 14, 2017
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I was checking for a motherboard for my 5820K and in the compatibility list I saw 2 variants of the cpu.

1. Core i7-5820K(3.3G,140W,L3:15M,6C,HT)
2. Core i7-5820K (3.3GHz, L3:15M, 6C, HT, 140W, rev.R2)

Never heard of that before. Is it a thing?
I might have the first one that isn't compatible with the latest M/B? The Box and stickers doesn't say R2 nowhere.
How can I tell? Distinguish between them (without using any software since I don't have a motherboard yet?
Are then any differences?