but it would be preforming like the "490"
Would it?
I mean, 36 Cu > 40 Cu = +11%.
1266Mhz =>... dunno, let's be generous, +100Mhz, so 7.8% increase here.
In case it scales perfectly (there is mem and other things) +11% * +7.8% = ~20% increase.
So if base is C7 with 18090 score, we get to 21687, which is between 980Ti and TitaniumX, still rather short of 1070.
However, 380 and 380 difference in 3DMark was about 9%.
So if we drop clock boost, it's 18090 => 20099, roughly at Ti levels (and likely doable with the same 6 pin power connector).
I'd expect 490 to take on 1070 and 490x to take on 1080, the way 390 and 390x did. (Vega 10)