New Build: Questions for Crossfire R9 390x

[Kubiks]

Hi everyone!

 

This is my first post on the forums, but I have been a long time lurker.  This place is a great source of info and has helped me immensely in the building of my newest pc.  A lot has changed since 2004 when I built the last!

 

The new system looks like this:

 

MSI Gaming 7 Z97 mobo

Core I7 4790k

MSI Radeon R9 390x

Swiftech H220x cooling loop

16 Hyper X beast 2400 ddr 3

250 Gb Patriot SSD

1tb Seagate HDD

850 watt EVGA Supernova Gold Rated PSU

All in a Fractal Designs Define R4 case

 

My question is about Crossfire.   I want to run two 390x's.

 

 So this would be my first time using multiple GPUS.  I've already checked on the power consumption for the two 390X's using several utilities.  Im seeing anything from 740 to 780 at full load.  It would probably be best to upgrade the PSU to somethign closer to 1000 soon , but is a brand new 850 gold sufficient for the short term?  I also think that when giving a small overclock to the CPU (something around 4.7 to 4.8 in the future, when needed) I will need a larger psu for that as well?

 

When it comes to PCI E slots, Im noticing on my board and many others with the z97 chipset, that there is one 16x slot, but can also run two x8 and it looks like 3 or 4  x4.  This is where I start to get a bit confused.  Are there any boards with this chipset that have two 16x slots?  All these cool SLI and CF builds im seeing, are they running at the lower lane bandwidths? 

 

I guess what I am really getting at is this:  Are the numbers just tripping me up, or when i see builds like where  Linus puts several Titans in a machine, are they all running at like three 4x pci speed?

 

If anyone has info or links to a great guide that you would recommend for Crossfire beginners, please let me know!

 

I searched on the forums already, but didn't come up with anything relevant to my question.  Im going to say thanks in advance if anyone can help, and I apologize for my lack of knowledge with the newer components.  Last build that I did had a Ti 4600 in it, so you see how long ago that was!

[thekeemo]

850w is all you need

[Flowroro]

A 2x 16x slot is usually 16x lane and a 8x lane. If you xfire it will scale down to the lowest lane automatically

8-8 pcie lanes are good for sli, 16-16 are more expensive and they make like a few fps difference at most. I've also heard of some stuttering and delays using 16-16. But that's for sli. Xfire not too sure about but performance wise not much of an increase.

(Just a tip)

[Flowroro]

So when ur picking out a mobo don't be too worried about pcie lane speeds

[Kubiks]

Ok, thanks.  That was a fast bunch of responses.  I will check for more info in the morning.

[SkilledRebuilds]

Ok, thanks.  That was a fast bunch of responses.  I will check for more info in the morning.

http://linustechtips.com/main/topic/168268-r9-290-crossfire-total-system-power-consumption-ax860i-results-at-different-overclock-speeds-water-cooled/

Power consumption graphs for Crossfired 290's

860w PSU for 2x 290's (Watercooled, uses less than Air)

[DXMember]

Your 4790k will have only 16 PCI-E lanes - so x8/x8 is all you can dream of in crossfire.

The board will have multiple x16 PCI-E slots physically, but electrically only the first one will be x16, the second will be x8 and the rest will probably be x4 both electrically and physically.

If you run single card it will be x16/x0

If you run crossfire it will be x8/x8

Does that make sense?

 

If you want three (or more cards) you will have to cash out for X99 board with a CPU that will have 28 PCI-E lanes or 40 PCI-E lanes.

 

 

And all you need is a quality 850W powersupply.

I would recomend SS-860XP

[Curufinwe_wins]

I should mention you gotta make sure your airflow is exquisite because two 300W TDP gpus get really really hot in cf.

Hawaii is kinda a bitch. On topic though I'd say 850 is the absolute minimum. Two Hawaii's plus an overclocked 4790k like that will draw by themselves around 800 W peak and the rest of the build (mainly mobo) is normally estimated at 100-200W for me personally I wouldn't be comfortable with Hawaii cf using less than a 1000W psu.

[Kubiks]

Awesome.  Great input. Thank you all.  I was reading an article on how the 390x in CF scales pretty damn well with CF compatible games.  I saw some great results in the 4k range too, which is where Im looking to go.   I think Ill pull the trigger.  I've heard that crossfire can now run without the bridge, but directly through the pci lanes, is that true?

[Curufinwe_wins]

Awesome. Great input. Thank you all. I was reading an article on how the 390x in CF scales pretty damn well with CF compatible games. I saw some great results in the 4k range too, which is where Im looking to go. I think Ill pull the trigger. I've heard that crossfire can now run without the bridge, but directly through the pci lanes, is that true?

Yea the amd version doesn't use a bridge. I mean it's not without flaws but yay one less part sitting around.

[lxyfutures]

850w PSU is big enough even if you OC you cpu, You will run 8X+8X pci/e line perfectly so don't worry. 2 390x is the best choice to play 3A games on 4K this days, it can do great job as well. Although if you don't play AAAgames, one will be enough

[Curufinwe_wins]

850w PSU is big enough even if you OC you cpu, You will run 8X+8X pci/e line perfectly so don't worry. 2 390x is the best choice to play 3A games on 4K this days, it can do great job as well. Although if you don't play AAAgames, one will be enough

That isn't really accurate. Each 390x peaks pretty often around 300 W (at stock...) and an overclock of even 4.8 increases cpu power consumption by almost double from 4.2/4.4 (depending on mobo the 4 core turbo clock actually does vary), which doesn't leave much if any room for other components. It should be enough (if the PSU is good), but it isn't close to comfortable by any stretch of the imagination.

 

Also going above 90% load on a PSU really isn't generally a good idea.

[Kubiks]

I jsut wanted to add to this, as I've had some time to tinker around with my system and the crossfire msi r9 390x setup.  The two cards ran on the 850 watt evga power supply, but would sometimes under benchmark conditions (and metro last  light) trip the max power and hsut hte system down.  I recently upgraded to a corsair rm1000i psu, and with the corsair link software, I can see that the whole pull up to 900 watts max.  That is with a cpu overclock, and both gpus overclocked as well.  Keep in mind, I also have a swiftech h220x made into a custom loop. 

 

I wanted to add this info out there, as an 850 watt was not sufficient for running a crossfire 390x setup.   I would advise anyone that is doing a build similar to this to get a 1000watt psu or a 1200 watt psu.   Now everything is stable.   There is plenty of headroom if i run the cards at standard clocks, even with the 4790k set to 4.8 @ 1.21v. 1.23v

Edited October 8, 2015 by Kubiks

[Prysin]

AMDs Bridgeless Crossfire is rated to run at 2x 8x PCIe GEN2.0

 

so if you can run 2x 8x PCIe GEN3.0 then you are more then good to go (PCIe gen3 is twice as fast as gen2... so 8x PCIe 3.0 is technically just as fast as 16x PCIe 2.0)

[Curufinwe_wins]

I jsut wanted to add to this, as I've had some time to tinker around with my system and the crossfire msi r9 390x setup.  The two cards ran on the 850 watt evga power supply, but would sometimes under benchmark conditions (and metro last  light) trip the max power and hsut hte system down.  I recently upgraded to a corsair rm1000i psu, and with the corsair link software, I can see that the whole pull up to 900 watts max.  That is with a cpu overclock, and both gpus overclocked as well.  Keep in mind, I also have a swiftech h220x made into a custom loop. 

 

I wanted to add this info out there, as an 850 watt was not sufficient for running a crossfire 390x setup.   I would advise anyone that is doing a build similar to this to get a 1000watt psu or a 1200 watt psu.   Now everything is stable.   There is plenty of headroom if i run the cards at standard clocks, even with the 4790k set to 4.8 @ 1.21v. 1.23v

Called it.

[Prysin]

Called it.

yeah, 1200w is what i would say is the minimum anyway...

 

why?

because you do not want to load your PSU to 100% anyway... and the AX1200i is relatively cheap, while offering a damn good conversion rate and number of 8pin inputs/outputs

[Curufinwe_wins]

yeah, 1200w is what i would say is the minimum anyway...

 

why?

because you do not want to load your PSU to 100% anyway... and the AX1200i is relatively cheap, while offering a damn good conversion rate and number of 8pin inputs/outputs

I mean if the PSU OP had didn't trip at power load then he probably would have been ok as long as he stopped stress testing haha.

[Prysin]

I mean if the PSU OP had didn't trip at power load then he probably would have been ok as long as he stopped stress testing haha.

true, but in the first place, staying at 100% PSU load will wear out the PSU and worsen the conversion rate over time....

 

Heat = resistance

resistance = bad performance

 

that is part of the basics of electrotechnical teachings.

[Curufinwe_wins]

true, but in the first place, staying at 100% PSU load will wear out the PSU and worsen the conversion rate over time....

 

Heat = resistance

resistance = bad performance

 

that is part of the basics of electrotechnical teachings.

Indeed. #post12

[Kubiks]

Called it.

You sure did.

 

And i wanted to add to the post so that others know.  I see a lot of bad information regarding crossfire and sli and psus.  People are saying "meh, youll be good to go, dont worry about it" when they are actually flirting with disaster.  Many people said the cards only drew 304 watts max , so oud be good with a 600..... Totally misleading information

[Kubiks]

I love the setup though, and its working perfectly now.  I just pulled a 20,000 on firestrike with the two cards and cpu overclocked. 

 

Thanks for all the input in the original post/