7970 CF or 7990?

[alz3abi]

Hi guys, i just want to know from previous model which usually perform better single card in CF or dual GPU like 7990 and why?

 

[wolfram23]

Crossfiring independent cards is almost always faster.

The problem with current X2 cards is that they reach the wattage ceiling for a single PCIe card, so they need to be underclocked in order to stay under ~350W. On the other hand, two independent cards would be able to each use that much power, so of course there is much more headroom. A single 7970 uses something like 200-225W I think, so obviously running two of them on a single card at stock speeds would greatly exceed the max power it can draw.

 

[alz3abi]

Crossfiring independent cards is almost always faster.

The problem with current X2 cards is that they reach the wattage ceiling for a single PCIe card, so they need to be underclocked in order to stay under ~350W. On the other hand, two independent cards would be able to each use that much power, so of course there is much more headroom. A single 7970 uses something like 200-225W I think, so obviously running two of them on a single card at stock speeds would greatly exceed the max power it can draw.

i didnt done any CF before and my current VGA is 4870X2 , i usually avoid CF/SlI because if i wasnt mistaken the lane of PCI-E was 1 16X and other usualy 8X -> 4X.

what i heard you will not use the secondary card full power, im not sure about the new motherboards or new PCI-e 3.0 if this issue solved.

 

[alz3abi]

Crossfiring independent cards is almost always faster.

The problem with current X2 cards is that they reach the wattage ceiling for a single PCIe card, so they need to be underclocked in order to stay under ~350W. On the other hand, two independent cards would be able to each use that much power, so of course there is much more headroom. A single 7970 uses something like 200-225W I think, so obviously running two of them on a single card at stock speeds would greatly exceed the max power it can draw.

i didnt done any CF before and my current VGA is 4870X2 , i usually avoid CF/SlI because if i wasnt mistaken the lane of PCI-E was 1 16X and other usualy 8X -> 4X.

what i heard you will not use the secondary card full power, im not sure about the new motherboards or new PCI-e 3.0 if this issue solved.


i have another question , what is the different between XDR2 and GDDR5 in term of performance?

 

[Gordon Freeman]

Crossfiring independent cards is almost always faster.

The problem with current X2 cards is that they reach the wattage ceiling for a single PCIe card, so they need to be underclocked in order to stay under ~350W. On the other hand, two independent cards would be able to each use that much power, so of course there is much more headroom. A single 7970 uses something like 200-225W I think, so obviously running two of them on a single card at stock speeds would greatly exceed the max power it can draw.

I think it has more to do with heat output and not power draw.

 

[bystander]

i didnt done any CF before and my current VGA is 4870X2 , i usually avoid CF/SlI because if i wasnt mistaken the lane of PCI-E was 1 16X and other usualy 8X -> 4X.

what i heard you will not use the secondary card full power, im not sure about the new motherboards or new PCI-e 3.0 if this issue solved.


i have another question , what is the different between XDR2 and GDDR5 in term of performance?

Just to be clear and make sure you undestand, you ARE using crossfire with the 4870x2. It's just that the crossfire takes place on a single card. That means you experience all the same drawbacks associated with crossfire.

 

[wolfram23]

A PCIe slot provides up to 75W, a 6 pin up to 75W, and an 8 pin up to 100W. So PCIe + 2x 8-pin connectors is 375W max. Of course, some PSUs will be able to deliver more, but manufacturers need to conform to specs.

AMD offers "PowerTune" on their big cards, for example the 6990. With it set to +20% you are able to draw up to 450W max which opens OC headroom, but again, PCIe specs limit you to at most 375W at default.

Heat is of course going to be an issue as well with that much power.

 

[alz3abi]

A PCIe slot provides up to 75W, a 6 pin up to 75W, and an 8 pin up to 100W. So PCIe + 2x 8-pin connectors is 375W max. Of course, some PSUs will be able to deliver more, but manufacturers need to conform to specs.

AMD offers "PowerTune" on their big cards, for example the 6990. With it set to +20% you are able to draw up to 450W max which opens OC headroom, but again, PCIe specs limit you to at most 375W at default.

Heat is of course going to be an issue as well with that much power.

when u are talking about heat ~ what is the avg heat you should expect in IDLE?

currently im getting 85C no load only windows and some application but not graphical fan at auto

my graphics card is 4870X2 default clocking

 

[wolfram23]

85C would be very high under max load. Usually idle is anywhere from 35C to 50C, depending on circumstances. Mine idle around 40C.

You probably haven't cleaned your PC in a while. Buy a compressed air duster, open the case, and blast out your gpu and CPU heatsinks.

 

[Gordon Freeman]

A PCIe slot provides up to 75W, a 6 pin up to 75W, and an 8 pin up to 100W. So PCIe + 2x 8-pin connectors is 375W max. Of course, some PSUs will be able to deliver more, but manufacturers need to conform to specs.

AMD offers "PowerTune" on their big cards, for example the 6990. With it set to +20% you are able to draw up to 450W max which opens OC headroom, but again, PCIe specs limit you to at most 375W at default.

Heat is of course going to be an issue as well with that much power.

Heat is the problem and is it wasn't than PSU manufactures would be making PSUs that allow the dual GPU cars like 6990 and 590 to draw all the power they could use but thermal limits is already an issue with stock air cooling which is why Radeon and Nvdia routinely under clock there dual GPU cards. Two GPUs and inch away from each other on one printed circuit board lend themselves to thermal cooling issues which is why it is always better to just get single cards for CF/SLI because then the thermal limit envelops are within spec and therefore in turn the cards can be pushed to there max limit allowable buy there respective architectures without overheating issues like a dual GPU.

 

[Gordon Freeman]

85C would be very high under max load. Usually idle is anywhere from 35C to 50C, depending on circumstances. Mine idle around 40C.

You probably haven't cleaned your PC in a while. Buy a compressed air duster, open the case, and blast out your gpu and CPU heatsinks.

4870x2 routinely goes past 100c when gaming.

 

[alz3abi]

4870x2 routinely goes past 100c when gaming.

it look like normal when gaming it still 80s but the fan become noise and it reach around 50~65% speed

 

[wolfram23]

Heat is the problem and is it wasn't than PSU manufactures would be making PSUs that allow the dual GPU cars like 6990 and 590 to draw all the power they could use but thermal limits is already an issue with stock air cooling which is why Radeon and Nvdia routinely under clock there dual GPU cards. Two GPUs and inch away from each other on one printed circuit board lend themselves to thermal cooling issues which is why it is always better to just get single cards for CF/SLI because then the thermal limit envelops are within spec and therefore in turn the cards can be pushed to there max limit allowable buy there respective architectures without overheating issues like a dual GPU.

Says you.

Power

PCI Express cards are allowed a maximum power consumption of 25W (×1: 10W for power-up). Low profile cards are limited to 10W (×16 to 25W). PCI Express Graphics (PEG) cards may increase power (from slot) to 75W after configuration (3.3V/3A + 12V/5.5A).[8] Optional connectors add 75W (6-pin) or 150W (8-pin) power for up to 300W total.

Says the PCIe specifications.
http://en.wikipedia.org/wiki/PCI_Express

 

[phamhlam]

Get Nvidia. SLI 670 would beat Xfire 7970.

 

[Gordon Freeman]

Says you.

Power

PCI Express cards are allowed a maximum power consumption of 25W (×1: 10W for power-up). Low profile cards are limited to 10W (×16 to 25W). PCI Express Graphics (PEG) cards may increase power (from slot) to 75W after configuration (3.3V/3A + 12V/5.5A).[8] Optional connectors add 75W (6-pin) or 150W (8-pin) power for up to 300W total.

Says the PCIe specifications.
http://en.wikipedia.org/wiki/PCI_Express

to much Heat is a big issue with dual GPU cards since they started making them this is a well known fact and this is even when the cards have been factory undervolted LOL.

 

[Gordon Freeman]

Get Nvidia. SLI 670 would beat Xfire 7970.

570 SLI and 6950 CF are already faster than a 7970 6870 CF is as fast as 7970 currently the new cards from Nvdia will have to add tons of budget minded value for them to be competitive cause there is already ample performance available on the market for GPUs.

 

[Pinhedd]

I think it has more to do with heat output and not power draw.

Heat output and power draw are the same thing. All power drawn by a card is either dissipated as heat or transferred as part of a signal to another device such as a monitor. The amount of power transferred to a monitor is absolutely negligible.

 

[Gordon Freeman]

Says you.

Power

PCI Express cards are allowed a maximum power consumption of 25W (×1: 10W for power-up). Low profile cards are limited to 10W (×16 to 25W). PCI Express Graphics (PEG) cards may increase power (from slot) to 75W after configuration (3.3V/3A + 12V/5.5A).[8] Optional connectors add 75W (6-pin) or 150W (8-pin) power for up to 300W total.

Says the PCIe specifications.
http://en.wikipedia.org/wiki/PCI_Express

6990 is two undervolted 6970s and all ready even being undervolted heat is an issue so how does 8pin 105watts and 6pin 75watts PCI-E power have to do with anything when the thermal design is just inefficient even when underclocked and volted on dual GPU cards which is why they are flawed LOL.

 

[wolfram23]

to much Heat is a big issue with dual GPU cards since they started making them this is a well known fact and this is even when the cards have been factory undervolted LOL.

No ***, Sherlock.

The cards still need to conform to specifications. Do you know what specifications are? They are rules that must be obeyed or else they do not get certified, and that means they do not get sold. If they want to sell their cards, they need to conform. Hence there is a power limitation.

The difference from idle to load is around 280W for the 7970. Give the CPU 80W (on the high side) and you're talking 200W for a single GPU. Make a dual card out of that, you're at 400W. Guess what. You can't sell that card. You have to underclock and undervolt it to drop the power by 100W.

Now look at load temps. The difference between a 6970 power and 6990 power is about 175W and the difference in temperature is only 6C at 88C max. 88C isn't that bad, they have thermal headroom. What they do not have is power headroom because they have to conform to specs!

 

[Gordon Freeman]

Heat output and power draw are the same thing. All power drawn by a card is either dissipated as heat or transferred as part of a signal to another device such as a monitor. The amount of power transferred to a monitor is absolutely negligible.

Electrically produced heat is a waste by product of inefficiency hence why typically newer cards are more powerful using less energy and heat. The 80+ PSU certification explains thermal efficiency very well. http://en.wikipedia.org/wiki/80_PLUS in short Heat output and power draw are directly influenced by the efficiency of the GPU architecture for example GTX 480 vs GTX 580 the GTX 480 creates lots more wasted heat energy because it was very inefficient.

 

[Gordon Freeman]

No ***, Sherlock.

The cards still need to conform to specifications. Do you know what specifications are? They are rules that must be obeyed or else they do not get certified, and that means they do not get sold. If they want to sell their cards, they need to conform. Hence there is a power limitation.

http://images.anandtech.com/graphs/graph5261/43136.png
http://images.anandtech.com/graphs/graph5261/43137.png

The difference from idle to load is around 280W for the 7970. Give the CPU 80W (on the high side) and you're talking 200W for a single GPU. Make a dual card out of that, you're at 400W. Guess what. You can't sell that card. You have to underclock and undervolt it to drop the power by 100W.

http://images.anandtech.com/graphs/graph5261/43140.png

Now look at load temps. The difference between a 6970 power and 6990 power is about 175W and the difference in temperature is only 6C at 88C max. 88C isn't that bad, they have thermal headroom. What they do not have is power headroom because they have to conform to specs!

It has to do with HEAT which is why they cripple the dual cards not because of PCI-E standards cause they could just as easily put on 4 8pin power dongles on the 6990 etc but they didn't cause of the heat Thermal issues it would incur.

 

[wolfram23]

It has to do with HEAT which is why they cripple the dual cards not because of PCI-E standards cause they could just as easily put on 4 8pin power dongles on the 6990 etc but they didn't cause of the heat Thermal issues it would incur.

Are you a moron? Have you bothered to read anything? The PCIe standard does not let them put 4 8-pin connectors on it! At most they get two, and 300W! That is it!

You're also convinced a 560 Ti is slower than a 6870, though, so I guess I should take it easy on you. It's not nice to make fun of the mentally challenged.

 

[Gordon Freeman]

Are you a moron? Have you bothered to read anything? The PCIe standard does not let them put 4 8-pin connectors on it! At most they get two, and 300W! That is it!

You're also convinced a 560 Ti is slower than a 6870, though, so I guess I should take it easy on you. It's not nice to make fun of the mentally challenged.

Whom said they could not put more power dongles on a GPU if they really wanted or needed to there is no PCI-E standard inhibiting how many PCI-E power plugs can be wired into a Dual GPU however there are thermal limit issues which is why they dont so stop being sore cause you are wrong LOL. PS I never stated that about the 560ti

 

[Gordon Freeman]

Are you a moron? Have you bothered to read anything? The PCIe standard does not let them put 4 8-pin connectors on it! At most they get two, and 300W! That is it!

You're also convinced a 560 Ti is slower than a 6870, though, so I guess I should take it easy on you. It's not nice to make fun of the mentally challenged.

http://pcper.com/image/view/6686?return=node%2F52216