Questions About Crossfire

[poofyhairguy]

In preparation for the 480 release I have some questions about Crossfire. I know things might change for the Polaris cards, so let's assume that things will remain the same as today for the purpose of the thread.

Primary Question:

Can you Crossfire two different models of the same card? Like one 290 is a factory OCed card with a third party cooler and the other 290 is a boring reference card will they still work together fine? What if one has more RAM or a better power delivery?

Follow up questions if primary question answer is "yes:"

1. If they do work together, are you restricted to the speed of the slowest card (aka does OCing one of the two cards do anything for you)?

2. In the case that you run across games that don't support Crossfire is there some slick way to turn Crossfire on and off or is the game just a mess until you go dig in driver settings? Is there maybe some way to not only turn one card off but overclock the card left on non-Crossfire mode via scripting or something like that?

Thank you in advance for any responses.

 

[3DVagabond]

Not sure about #2

You can use cards from different vendors. They don't have to be the same clocks and you will get performance improvement from O/C'ing one. If they have different memory amounts it will default to the lower amount. You can even crossfire a 290 with a 290X and it will give you extra performance from the 290X over a 2nd 290.

 

[Shmee]

You can turn off crossfire in the radeon crimson profile for your individual game.

 

[Headfoot]

3d answered 1. 2 is yes, you can set Crossfire per-application and there is also a global crossfire toggle. I've found crossfire per application is a little sketchy and doesnt always work. Its been improving since they implemented it. The global crossfire toggle works just fine though.

 

[IEC]

Having run up to tri-fire 290 configurations previously, some with different clocks...

1. No, not restricted - OCing one card over the other does result in a performance uplift versus the 2x at the slow clock
2. You can set up an individual profile per game in Crimson and disable Crossfire.

I'll probably be an early adopter of triple Crossfire RX 480s so I'll let you know how that goes. It'll be interesting to use basically the same amount of power for 3x RX 480s as I currently do when I run my single remaining R9 290 at max OC.

Edit: Reviews are out. Bought 2x 4GB RX 480s @ 199.99 each.

 

[guskline]

Having run up to tri-fire 290 configurations previously, some with different clocks...

1. No, not restricted - OCing one card over the other does result in a performance uplift versus the 2x at the slow clock
2. You can set up an individual profile per game in Crimson and disable Crossfire.

I'll probably be an early adopter of triple Crossfire RX 480s so I'll let you know how that goes. It'll be interesting to use basically the same amount of power for 3x RX 480s as I currently do when I run my single remaining R9 290 at max OC.

Will you use the 8G version?

 

[IEC]

Will you use the 8G version?

Doesn't seem like the 4GB version will be available in much quantity initially as far as I can tell. So I will most likely be using the 8GB version.

Once custom AIB cards are released and reviews of those are out I will likely swap for those and relegate the reference cards to mining duty.

 

[thesmokingman]

Primary Question:

Can you Crossfire two different models of the same card? Like one 290 is a factory OCed card with a third party cooler and the other 290 is a boring reference card will they still work together fine? What if one has more RAM or a better power delivery?

Follow up questions if primary question answer is "yes:"

1. If they do work together, are you restricted to the speed of the slowest card (aka does OCing one of the two cards do anything for you)?

2. In the case that you run across games that don't support Crossfire is there some slick way to turn Crossfire on and off or is the game just a mess until you go dig in driver settings? Is there maybe some way to not only turn one card off but overclock the card left on non-Crossfire mode via scripting or something like that?

Thank you in advance for any responses.

Yes

1. Crossfire like 6 years ago was locked via clockspeeds, but with the advent of GCN and frame pacing, it's not anymore. In fact yall should stop thinking about it in terms of clock speeds and instead in terms of latency. Clock speeds don't matter, the cards latencies will be synced via frame pacing so whatever differences in speeds will be timed to provide the best frametimes. But to sum up your answer, clocks have not been locked for since the GCN came into existence. Moving on, ideally you want the cards at teh same speed to minimize how much frame pacing has to work to match the cards latencies.

2. You can override built in profiles to manually force a different cfx profile, or to disable crossfire altogether for that game.