290x CF vs 290x + 390x

So I have a 290x 4gb card atm, and my question is what if any difference in performance would I see between crossfire of 2 290x's vs a 290x and a 390x? I understand that I will only be able to use 4gb from the 390x. I haven't really been able to find benchmarks of 290xCF vs 290x and 390x maybe my google skills are weak, any foresight on this would be awesome.

The 390x will run at 290x speed.

you will find a 290x for cheaper so I would go with that option.

you will see a considerable performance gap though I don't think you would want to do Crossfire. for a few reasons. the new Crimson updates doesn't support it at the moment..

AND you can do yourself good by selling the 290X and with the money you are willing to spend on the 390X go pick up a R9 Fury. the performance is much better and you won't have to deal with Crossfire headaches in some games.

what do you mean by considerable performance gap? and unfortunitly the fury is out of my range at this point its like 500$ where as a 390x is 360~ and the 290x is 320~

Scaling with AMD cards is insane. You're going to see a big performance gap. what I mean by that is, you will see probably double the performance in most cases. as compared to just running one 290x.

That dosent really help answer my question though haha

No, this is wrong. That's only w/ SLI. Each card will run at its specified frequency however I do believe RAM isn't stackable so your left with the RAM of the first card. That said, I'd get another 290X second hand.

OP, with an OC absolutely no difference.

That said a 390X will achieve higher speeds but seeing as you couldn't fully utilize the VRAM I doubt an OCed 290X would fall too short. It wouldn't be worth the price premium

I was just bring it it to your attention lol

I personally wouldn't recommend Crossfire that's all :(

If I were in your shoes and I wanted the upgrade I'd sell the 290x and pick up a R9 Fury. because if you tried the Crossfiring the 390X with a 290X what will happen is Crossfire is going to use the card with the lowest VRAM. in your case, the 290X. so realistically speaking buying a 390X for crossfire is a waste of money. cause you're not really using all the VRAM (Which realistically you won't anyways even if you sold the 290x for the 390X regardless) despite it running at it's normal clockspeeds. and there are issues that come with Crossfire to begin with despite the massive performance gains.

While there are issues, I don't think it would be worth the hassle. When it is utilized, the OP would see higher performance without a doubt. The only reason not to is that some things won't use it, increased heat, and you'd need at bare minimum a 850w PSU delivering at least 31 amps.

Exactly there are just too much headaches. I mean they aren't much but if you already have the PSU that does it. but I've had personal experience with Crossfire, Massive tearing, sometimes the second card doesn't get fully utilized, as you mentioned the extra heat, and believe it or not, the anger of trying to get both cards to run at the same clockspeeds. lol back when I had two 270X cards. one card would OC to 1200mhz the other wouldn't go past 1170mhz on the core. the anger was real.

so the consensus is other than to just get a fury lol, that the 390x will not give me any extra performance in CF than another 290x?

It would utilize the max OC of each card though. I understand where you're coming from

No you'll get a massive performance gain no doubt about it. but you're not going to get 8GIBS of VRAM to use regardless of how you set up the cards.

Yes and no lol. A 390x will run you $100 or so more yet would yield maybe 2 frames at most when all cards are overclocked

a 390x is only 40$ more atm that's the only reason I'm considering it

I'd go for it then unless you can get a 290X second hand.

Go with 290x CF its cheaper and same level of performance