• Welcome to Overclockers Forums! Join us to reply in threads, receive reduced ads, and to customize your site experience!

Crossfire question.

Overclockers is supported by our readers. When you click a link to make a purchase, we may earn a commission. Learn More.

Cojac92

Member
Joined
Jun 26, 2011
Location
South Carolina
I was planning on getting a 7970 soon, but I found a deal I couldn't pass up on another 6870. I may still get a 7970 later on, I'll have to see what kind of performance I get out of these two cards.

My current 6870's stock clocks are 900 core and 1050 memory. The 6870 I'm getting next week is 920 core and 1120 memory. So my question is, what card should go in what PCI slot? One will auto-overclock or either auto-underclock the other card... right?
 
Nevermind the slots.
The faster will downclock.
Can bring freq up with Trixx or MSI AB.

Sorry: using mbile.
 
Nevermind the slots.
The faster will downclock.
Can bring freq up with Trixx or MSI AB.

Sorry: using mbile.

Alright, cool deal.

The reason I asked about the slots is I heard somewhere that depending on what slot it was in (top or bottom) that would result in the OC or underclock in order to match the other cards speed. Although, that probably didn't come for a reliable source.

Thanks for the info!
 
The 6870's will definitely outperform the 7970, the only downside is extra power draw.

As for slots, you don't really need to worry as manu mentioned you can easily clock the other card to the higher specs since the difference is minimal ;)
 
The 6870's will definitely outperform the 7970, the only downside is extra power draw.

We are only talking about 2 $180 video cards here. How will they outperform a 7970? A lot of games don't even give full scaling in crossfire, correct?
 
We are only talking about 2 $180 video cards here. How will they outperform a 7970? A lot of games don't even give full scaling in crossfire, correct?

Most games have excellent scaling so that is not a major issue, the 6850's when considered in pure computing power will be faster than a 7970 but by a very small margin. However at higher resolutions/benchmarks the 7970 will perform better due to the extra vram.

As you mentioned the only downside to xfire setups is that all games will not give 100% scaling, which is why single cards are preferred along with lower power consumption.
 
Last edited:
How well do you think two 6870's will perform in an Eyefinity setup? I was going to get 2 more monitors when I ordered my 7970. I've seen a good many Eyefinity reviews on a single 7970, and it seems pretty solid.

Although, I haven't seen many crossfire 6870 Eyefinity setups.

The resolution I want to attempt is 5760x1080.
 
If going Eyefinity, you definitely need the 2GB vram.

BUT it won't be enough to play the games at ultra settings. If you want to, you need a 7970/7950 xFire.
 
How well do you think two 6870's will perform in an Eyefinity setup? I was going to get 2 more monitors when I ordered my 7970. I've seen a good many Eyefinity reviews on a single 7970, and it seems pretty solid.

Although, I haven't seen many crossfire 6870 Eyefinity setups.

The resolution I want to attempt is 5760x1080.

hello!!
I have 2 xfx 6870 in crossfire, and depending on games I can play well in eyefinity or not. I play crysis in 2400x900 it's not bad, even if I don't see every detail, but the 1 gb ram is absolutely the bottleneck.

I don't suggest you 2 6870 if you wanna play the latest games on eyefinity.

In crysis2 I play with about 80-120 fps not lower, with 4800x900 I cud play but would miss frames where there is action.

If I was you I would get a 7970, and then add another one in a while.


Anyway eyefinity rocks.
I recorded with fraps some c2 vids before my eyefinity, and cudn't wach them, I felt in a cage :D

If you want to know more tell me.
By the way, i find the cheapest 6870 for 159$ on Newegg.

These 2 cards were perfect in HD, I cud play on crysis2 on ultra with dx10, before the high res texture pack and before dx11. I do overclock them, to 980-1000, but keeping them on 70°C.

The upper one is a double fan one that when it spins at max is silent and cools down the second one, the second is a card with a stock cooler, has much more cooling potential but is much louder.


powercolor and club 3d did a double 6870, (like the 6990), and it's too bad they didn't put 4 gb ram in it, it would be a very strong card even for eyefinity.

I must tell you I believe there aren't cards to max out everything on a eyefinity setup like that and have playable fps (for me playable is above 80, no drops under 60, it must be fluid). Even not in triple or quad crossfire. Becouse of driver problems. Furthermore you have limits by pcie slots, and the cpu will bottleneck the cards.

I saw some testing with 4 gtx680 and the limit was by the cpu and pcie.


I'm telling you all this, becouse I do would like to play on highest settings, and there isn't yet a combo of cards that would do that on crossfire. The best I saw, in my opinion are the gigabyte 7970 OC windforce, with 3 fans, these run cooler and silent, averclock to 1300 mhz, but with one they reached 540 W powerdraw by the whole system. So my buy will be "to be upgraded", adding another card, and/or a better mobo/cpu. I have the asus p8p67 deluxe and 2600k, with 2 cards in cf, the pcie2 are already at 8x, wich in pcie3 is equal to 4x. At that speed, there is a bottleneck by it in some games, lowering fps by 5-20%.

Anyway... I would get the 7970, as soon as price drop :)

cheers
 
Last edited:
If going Eyefinity, you definitely need the 2GB vram.

BUT it won't be enough to play the games at ultra settings. If you want to, you need a 7970/7950 xFire.

I won't have to crossfire a 7970 or 7950 for Eyefinity. I've seen a lot of people getting 30-35fps @5760x1080 on Ultra in BF3. I could pull it back to high settings and get 50-60.

hello!!
I have 2 xfx 6870 in crossfire, and depending on games I can play well in eyefinity or not. I play crysis in 2400x900 it's not bad, even if I don't see every detail, but the 1 gb ram is absolutely the bottleneck.

I don't suggest you 2 6870 if you wanna play the latest games on eyefinity.

In crysis2 I play with about 80-120 fps not lower, with 4800x900 I cud play but would miss frames where there is action.

Furthermore you have limits by pcie slots, and the cpu will bottleneck the cards.


Anyway... I would get the 7970, as soon as price drop :)

Those resolutions are too low for me. When I buy two more monitors to match my current one I'll be at 5760x1080. Thanks for your crossfire resolution reference though.

My motherboard supports 16x - 8x - 4x. 2 way Crossfire/SLI will run at 8x-8x. I won't see a performance hit there, and my CPU won't be a bottleneck.

As far as 7970's dropping in price, I doubt they will. I read a couple articles a week ago in which AMD said that all 7 series cards won't see a price reduction for a quite a while.
 
I have two Sapphire Vapor-X 6870 1GB cards flashed to the TOXIC BIOS at 970/1150 and i'm getting a 3DMark11 score of P8853! Not all results will be the same because everyone has different CPU's RAM, mobo's etc... but two 6870's are still very powerful and will crush just most single cards.
 
30/35 is the average. Keep in mind that it will go to 20 and less on minimum.

Neither a single 7970 or a 680 can allow you to play BF3 with all the eye candies at 5760x1080 with a decent framerate.
 
I have two Sapphire Vapor-X 6870 1GB cards flashed to the TOXIC BIOS at 970/1150 and i'm getting a 3DMark11 score of P8853! Not all results will be the same because everyone has different CPU's RAM, mobo's etc... but two 6870's are still very powerful and will crush just most single cards.

Thanks for the reference!

30/35 is the average. Keep in mind that it will go to 20 and less on minimum.

Neither a single 7970 or a 680 can allow you to play BF3 with all the eye candies at 5760x1080 with a decent framerate.

Of course, but that's why I said I'd dial it back to high, and hopefully get around 50 average.

Luckily I don't notice lower frame rates. It seems to vary person to person. I have friends that can see SLI micro stuttering and stuff; I can't. I can also play games comfortably as low as 25fps. I will see only a small difference compared to 60 fps. (Varies by game though, with some games it is more noticeable at the same frame rates.)

I'll just see what the xfired 6870's do. I plan to get a 7970 regardless of the outcome with the 6870's. Just maybe sooner or later... depending on it.
 
Just dont try Trifire... the results kind of suck for what it costs i.e. crossfire is a much better bang for your buck. Not that you can trifire 6870's anyway... only one bridge port
 
I have two Sapphire Vapor-X 6870 1GB cards flashed to the TOXIC BIOS at 970/1150 and i'm getting a 3DMark11 score of P8853! Not all results will be the same because everyone has different CPU's RAM, mobo's etc... but two 6870's are still very powerful and will crush just most single cards.

I just did the 3dmark11 bench and get 8890, I just started the pc, after one hour stressing the cpu/gpu I would get a bit less I guess.

What do you mean with "flashed with the toxic bios"?

I have the core clock on 1000, I can't get higher, even not editign that ini file.

What do you get more with flashing the bios and what are the consequences?
 
Hi, I havent taken the time to read all of the other replies but i'd like to point out some things before you decide on crossfire.
I've recently added a 2nd 6870 to my build and these are some things I think are important to know:

1. make sure your card will fit in your case and the cooler wont block anything/cables

-I'm using aftermarket coolers to help my cards fit, one is a 3 slot cooler and the other is a 2 slot cooler

2. i experienced some heat problems when placing the cards next each other, the heat from one card would go into the fan of the other card. I ended up putting the second card in the farthest available slot. This is why I have a 3 slot and 2 slot cooler, otherwise it wouldn't fit in my full tower case.

3. Make sure you read up on the drivers and performance problems with crossfire. adding an extra card caused problems with Skyrim, Saints row 3, and some other games. These problems were somewhat solved with the driver updates, but for a while having one card was more than enough.

4. Be sure you really need the cards, a single 6870 can still run most things with out problems


I hope this helps
I realize that most people on these forums are familiar with frequent hardware changes, but even though i've built several systems I still ran into unforeseen problems that I am now sharing. Most of the time we only talk of performance and not some of the more physical aspects of installing new hardware.
 
I just did the 3dmark11 bench and get 8890, I just started the pc, after one hour stressing the cpu/gpu I would get a bit less I guess.

What do you mean with "flashed with the toxic bios"?

I have the core clock on 1000, I can't get higher, even not editign that ini file.

What do you get more with flashing the bios and what are the consequences?

The TOXIC model is the factory overclocked model from Sapphire, its just what the named it. Since the Sapphire Vapor-X and Toxic are nearly the same card except the difference in clocks I just used ATIWinFlash and flashed my Vapor-X's to the Toxic BIOS so that they would have all the same settings (the card now acts as if it is a TOXIC model and appears that way in ATI CCC).

Another reason I did this is because the two 6870's of the same model had different BIOS revisions and the clocks were a little different so I wanted them to be exactly the same for the crossfire configuration. I knew that the settings of the TOXIC model would be stable as well and I didn't really want to mess around with voltages and push the cards too hard.

Your score looks close to mine so I think you are good to go here. Flashing the BIOS is pretty easy but if you mess up you could turn your card into a paper weight.
 
I got my 2nd card today, just got done installing it. Crossfire is Enabled in CCC. I don't see the 2nd card in HWmonitor though. I'm about to fire up BF3 and do a short 60 sec benchmark and see what my average frame rate is now.
 
I'm having an issue already.... I ran the system fine for about an hour. Then I decided to run 3dmark vantage at stock clocks on my cards. Half way through I got a black screen. Rebooted it. Black screen again after windows login. I was using an HDMI cable, I switched to a DVI to see if that would solve the issue, and it didn't. Anyway, I'm running the new card I bought now. I am about to swap cards again and see if it will run fine on my old one.
 
I wiped all my CCC drivers, and profiles. Shut the system off. Installed both cards, power, and bridge. I went straight into windows fine. Downloaded the CCC suite, started installing it, and at around 60-70% I got a BSOD. Restarted my system, and now I get a teal screen with bars running through it after I login. I'm going to bed, I'll pick up with it tomorrow. Some help would be nice.
 
Back