CrossFireX Question

[Nik]

Is there a problem if I have two 4850's and one of them is a 512mb card and the other is a 1gb card?

CFX should just ignore the additional 512mb on the larger card, yeah? The memory difference between the two cards should be the only difference, yeah?

Catalyst says the cards aren't ideally matched but should still work.

Anyone know if this really is a problem or not?

 

[cusideabelincoln]

It will work, and it will act as if you have two 512MB cards. So it will ignore the extra RAM on the 1GB model. This shouldn't be a problem.

 

[Nik]

Then why does this happen?

http://forums.anandtech.com/me...id=32&threadid=2342596

If I have only 1 card in it seems to be fine. If I put both in and put the crossfire daughter cable on and launch eve or 3dmark06, I get wild psycho colors and it powers off.

 

[OCGuy]

I was inder the impression they needed the same amount of VRAM, but maybe that is just a nV thing.

 

[zagood]

PSU?

 

[cusideabelincoln]

81 C seems pretty damn hot for an idle card.

Heat would be seem to be the problem.

Next I would suspect the power supply.

And of course you can't rule out that one of the cards is faulty, unless you have already done so. Have you tested each card independently?

 

[F1shF4t]

You haven't mentioned the specs of your system.
Most important aspect what is your psu?

From your other thread, the second dial is gpu utilisation. When you took the picture was the gpu idle? If so thats very hot for idle temps. (Unless its the original 4850s with stock cooling, in that case you may need to up the fan speeps)

EDIT: As everyone mentioned 512 + 1024 will work fine. You'll effectivelly have 2*512 cards. I ran a similar setup with two 4870 before getting second 1024MB card.

 

[Nik]

Yes, I'm running the new card (1g) at the moment. If I run each card individually, I can run everything fine. If I run both cards at once it runs fine until I need something video intensive before it craps out.

I can't see the PSU sticker while it's installed, but it's nearly 700watts and I know it has an 80Plus rating. It's got two 6-pin connectors natively.

 

[Nik]

Originally posted by: F1shF4t
You haven't mentioned the specs of your system.
Most important aspect what is your psu?

From your other thread, the second dial is gpu utilisation. When you took the picture was the gpu idle? If so thats very hot for idle temps. (Unless its the original 4850s with stock cooling)

Yes, it was at idle, but that was the original card (512mb) that I've been using for quite a while just fine. The 512 card is only a 1u card so it's supposed to run hotter. The 1g card has a much bigger fan and is running about 35C idle

 

[v8envy]

Two 6 pin on a "700 watt" PSU is a red flag. Each of your 4850s should have two 6 pin connectors, which means you're using molex adapters to power your cards, correct?

Who is the manufacturer of your PSU, and what is the total rated wattage across all 12 volt rails?

 

[cusideabelincoln]

Have you tried using different Crossfire bridges, or using two at the same time?

 

[Nik]

Originally posted by: v8envy
Two 6 pin on a "700 watt" PSU is a red flag. Each of your 4850s should have two 6 pin connectors, which means you're using molex adapters to power your cards, correct?

Who is the manufacturer of your PSU, and what is the total rated wattage across all 12 volt rails?

I'd have to dismount the PSU to give you any more information.

Each of these 4850's only has ONE 6-pin connector, not two. Where are you getting that they should have 2?

 

[Nik]

Originally posted by: cusideabelincoln
Have you tried using different Crossfire bridges, or using two at the same time?

I only have one bridge.

 

[F1shF4t]

Originally posted by: v8envy
Two 6 pin on a "700 watt" PSU is a red flag. Each of your 4850s should have two 6 pin connectors, which means you're using molex adapters to power your cards, correct?

Who is the manufacturer of your PSU, and what is the total rated wattage across all 12 volt rails?

4850s have only one connector. The 700 watt with two pcie connectors sound suspect but for older units it was probably not uncommon.

Op try upping the fan speed on the stock 512 card. Which card do you use as primary, have you tried swaping them around? The hotter card will be better suited in the bottom slot.

 

[Nik]

Originally posted by: F1shF4t
Op try upping the fan speed on the stock 512 card. Which card do you use as primary, have you tried swaping them around? The hotter card will be better suited in the bottom slot.

I've tried them independantly, but the cooler card was indeed in the lower slot. I'll power down, pull the PSU and copy down stats, put both cards in with the hotter (512) the lower slot and cooler in the upper, and test things again.

...be right back

 

[Viper GTS]

This is indeed a very early 4850 (I sold it to him...). I bought it at BestBuy when they had them on sale right at launch, it's a VisionTek single slot cooler model. I had two and I seem to remember they both did ~80C idle, but were fine under load. Probably just a low fan speed.

Viper GTS

 

[Nik]

PSU: http://www.apevia.com/Products...asp?KEY=ATX-PFC680W-BK

 

[Nik]

Hmm. Interesting. I put the hotter card in the lower slot and I changed the bridge from the first "slot" to the second one. Things seem to be working (Eve doesn't crash, 3DMark06 doesn't crash).

 

[F1shF4t]

Originally posted by: Nik
PSU: http://www.apevia.com/Products...asp?KEY=ATX-PFC680W-BK

Hmm. That psu only has 330watts on the 12v rail. Depending what your other componensts are having 2*4850 on this thing may be pushing it. (If you have something like a quad core cpu then you would be pushing it)

Personally I would not run crossfire 4850s on that psu.

 

[F1shF4t]

Originally posted by: Nik
Hmm. Interesting. I put the hotter card in the lower slot and I changed the bridge from the first "slot" to the second one. Things seem to be working (Eve doesn't crash, 3DMark06 doesn't crash).

Could of been overheating. The top card cycles the hot air coming from the bottom one. If I use my msi card with the stock cooler in the top slot it'll hit some very high temps.

 

[Nik]

Originally posted by: F1shF4t

Originally posted by: Nik
PSU: http://www.apevia.com/Products...asp?KEY=ATX-PFC680W-BK

Hmm. That psu only has 330watts on the 12v rail. Depending what your other componensts are having 2*4850 on this thing may be pushing it. (If you have something like a quad core cpu then you would be pushing it)

Personally I would not run crossfire 4850s on that psu.

Yes, I have a quad core xeon.

Originally posted by: F1shF4t

Originally posted by: Nik
Hmm. Interesting. I put the hotter card in the lower slot and I changed the bridge from the first "slot" to the second one. Things seem to be working (Eve doesn't crash, 3DMark06 doesn't crash).

Could of been overheating. The top card cycles the hot air coming from the bottom one. If I use my msi card with the stock cooler in the top slot it'll hit some very high temps.

I checked and crossfire isn't running now. I have to reinstall the ATI driver. Basically it's still running on one card.

 

[Viper GTS]

I'd be interested to know how the CPU and PCIe power connectors are spread across the two 12V rails (if this thing actually is separate rails).

The fact that everything runs fine as long as you're only using one GPU (including when both are installed but crossfire is disabled) makes this whole thing smell of insufficient PSU.

Viper GTS

 

[F1shF4t]

Agree with Viper GTS on this one.

Each of the 4850s can use up to and over 100 watts of power. If you factor that the quad can use over 60 watts not including other components like mainboard hdds etc. That get very close to what the specs say the powersupply can output on the 12v rail (Most components use 12v rail nowdays)

 

[Nik]

After enabling crossfire again, it won't stay up. Crap.

Looks like I'm in the market for a new power supply. Again. :frown:

Thanks for the help, all.

 

[F1shF4t]

Originally posted by: Nik
After enabling crossfire again, it won't stay up. Crap.

Looks like I'm in the market for a new power supply. Again. :frown:

Thanks for the help, all.

For your machine a descent 550 - 650 watt psu would work fine. I'd recomend something like corsair units, I got 2 and no issues with them yet.

Also check out reviews before you buy. There are a lot of dodgy psus out there.