Sapphire 290 390 etc...
The Sapphire range of cards is one of the best! but I found a little confusion, I'll explain.
I've bought some used cards such as the Sapphire R9 290 (but I thought I'd bought an X version but had not)….the clock speed maybe a little higher ? (only_?_no other difference?)__would a Sapphire R9 290 "crossfire" with a 290 X ? - ditto that question for Sapphire 390/390 X.
The Sapphire range also has a tri-x name as well as the Nitro naming - (nitro_is_top_of_the_line)__and the two models have a different colour scheme.
I was after another 390 X (but someone had sold it already somewhere else)_then I found the 390 (not X)__so if Crossfire is to be attempted do both cards 100% have to be X variants? - Thanks