4870 Crossfire Performance Issues - Page 2 - Overclock.net

**Robilar** · 07-20-08

No its not the chipset. I ran the cards on a P5E as well.

That recommendation from ATI is the minimum. Again minimum with a power supply that can run at 80% load for extended periods of time.

I read a post from a fellow (its in german) that had your power supply and stuttering issues with a pair of 3870's in crossfire.

Seeing as you didn't get stuttering with a single card and the other people I have discussed CF4870's with are not getting stuttering, we can safely assume it is not crossfire or drivers.

rx7racer · 07-20-08

Quote:

Originally Posted by FrankyDeluxe

ATI itself recommends a 600W power supply for two 4870's in Crossfire mode, so again, i dont think thats the issue.

Yes offcourse. I got an X38 chipset, so that is not the problem.

I was just wondering if they are actually running x16, I know you have the ability and should be. Gotta cover all bases, there is something off somewhere I would say.

**Robilar** · 07-20-08

They do rx7. I ran my setup on the P5E X38 (until I sold it last week).

X38 and X48 provide full 16x16x bandwidth.

iggster · 07-20-08

heat issues? its either heat or power...

rx7racer · 07-20-08

Quote:

Originally Posted by Robilar

They do rx7. I ran my setup on the P5E X38 (until I sold it last week).

X38 and X48 provide full 16x16x bandwidth.

I haven't dug in the bios enough, but can you not adjust them? I though you could, or is that only for the ones that have 3 or more PCI-E x16 slots?

Anyway, stuttering is odd, I know the 3870X2 had that issue, but taht was for different reasons. I'm guessing you've reinstalled drivers.

Have you ran atitool and scanned just to see if the card #1 is 100% stable. You'll have to change the cards around in order to test both cards due to artifact tool only using one gpu.

Other then that I would run RBE up the fan speeds a bit and make sure you have good airflow. Flash the updated bios and see if that helps. You can raise the clocks and core volts using RBE also.

FrankyDeluxe · 07-20-08

Quote:

Originally Posted by Robilar

Right so given a 300w drain with a single card, add another 170 for two brings you up to 470w drain on a 600w power supply.

do you know how many power supplies can provide continuous power at 78% of their load?

not too many outside of the mainstream makers (for example, PC Power, Enermax, Seasonic, Corsair, Silverstone).

It's one thing for a power supply to be rated for example at 600w but the reality is that most systems do not draw anywhere near full load. If you look at tests done by sites like hardocp or jonny guru, they test power supplies typically at 80% of load for an extended period.

It's surprising how many power supplies don't pass these tests with flying colors.

This power supply has a nice diplay on the back that shows the actual usage, so i ran Crysis and ran around a bit. It peaked to 430W tops. Now i know a power supply never has a 100% efficiency, but if it's already at 100% capacity at 430W it means that it has a efficiency of less then 70%, which i don't believe is true.

rx7racer · 07-20-08

Quote:

Originally Posted by FrankyDeluxe

This power supply has a nice diplay on the back that shows the actual usage, so i ran Crysis and ran around a bit. It peaked to 430W tops. Now i know a power supply never has a 100% efficiency, but if it's already at 100% capacity at 430W it means that it has a efficiency of less then 75%, which i don't believe is true.

You'd be surprised what psu's fall short of that and some I have seen dip below 70%. I would think you would be getting some vlotage fluctuations then as well. If you have a multimeter check the 12v and 5v rails while runnig crysis and watch to see if they have some heavy or just really sporadic dips and fluctuations.

Especially after you factor in the age of the caps and other components of the psu and the duration it is usually left on. Their efficiency tends to deminish over time especially with higher loads nearing it's peek.

iggster · 07-20-08

Quote:

Originally Posted by FrankyDeluxe

This power supply has a nice diplay on the back that shows the actual usage, so i ran Crysis and ran around a bit. It peaked to 430W tops. Now i know a power supply never has a 100% efficiency, but if it's already at 100% capacity at 430W it means that it has a efficiency of less then 75%, which i don't believe is true.

but doesnt mean the cards are getting their proper voltage though. You need to get a DMM and check the voltage while playing a game (if you done it before if not then its not something a noob can do)

iggster · 07-20-08

Let me add, my 1200 power supply can barely power my gtx 280s when everything is overclocked, I go passed a certain point in clock speeds for the cards and in this one scene in vantage (second run where they fire the missiles at the planet) the fan on the power supply REALLY starts going and like 10 seconds later it starts studdering and if it gets bad enough it will crash. If I take out one card then I can overclock the cards like crazy without those affects.

FrankyDeluxe · 07-20-08

Quote:

Originally Posted by iggster

but doesnt mean the cards are getting their proper voltage though. You need to get a DMM and check the voltage while playing a game (if you done it before if not then its not something a noob can do)

Hmm. Well maybe you are right. I guess i have to RMA the card then

. I dont want to spend another 100 bucks for a new PSU at this moment. I still find it strange though, ATI recommends a 600W PSU which usually far more then required for safety cautions. What you are saying is that it is by far not enough, so that means that ATI is making serious false claims...

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4870 Crossfire Performance Issues

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