Judging by the amount of time we and fellow journalists spent asking questions about this new feature, we’ll try to take out time with this one and go for clarity. PowerTune is being pitched by ATI as a way to deliver more performance in typical applications by managing the maximum power draw of the GPU, and therefore the card. That’s true… from a certain point of view.
Just as Nvidia did with the GeForce GTX 570 1.3GB
and the GeForce GTX 580 1.5GB
, ATI has set an upper power draw limit for the two cards of the HD 6900-series. If at any time the GPU starts to consume any more than this, the GPU will automatically clock itself down to reduce the power draw. ATI says this allows it to set higher frequencies for its GPUs, as it no longer has to consider worst-case, thermal-virus-like applications.
For example, the HD 6970 2GB has a default frequency of 880MHz and it should run at this frequency whether it’s churning through World of Warcraft, Arma II or Bad Company 2. However, if the GPU should encounter something a little more taxing (and no, Crysis doesn’t count) the GPU might drop to a frequency of 800MHz. Previously, ATI would have had to set the frequency to 790MHz, but now it can deliver 90MHz more of gaming performance, hence the claims that PowerTune helps to deliver more performance.
Click to enlarge
However, there are a few differences between Nvidia’s and ATI’s technologies. For a start, ATI’s technology is entirely hardware-based. There are activity monitors in every part of the GPU, ‘based on an algorithm, we calculate how much power the GPU is actually drawing at any one time… By having [PowerTune] as something completely calculated on the GPU, this also means we can accommodate any future application that may have a higher power draw as well
’ Bauman told us.
Even better, ATI Catalyst Control Center gives you control over the maximum power draw of your graphics card. You can crank the upper limit up by 20 per cent to give the HD 6970 2GB the maximum 300W of the PCI Express 2.0 standard and allow maximum performance in even in the nastiest of applications (no, Crysis still doesn’t count). Alternatively, you could drop the power draw limit by up to 20 per cent to save power when playing undemanding games.
Twin BIOSes, Display Outputs and a Vapour Chamber Cooler
All HD 6900-series cards should have two BIOSes, as ATI thinks that a significant number of owners of high-end graphics cards like to flash their vBIOS with updated clock speeds and fan management profiles. Sometimes these vBIOS flashes go wrong, though, as you’re left with a particularly expensive desk ornament. A switch on a HD 6900-series card allows you to switch to a safe back-up vBIOS.
HIS and XFX managed to drop us some cards, and Sapphire has a
special bundle for its HD 6970 2GB card that we'll cover separately.
At this point it seems that the two vBIOS are distinct, and the safe vBIOS won’t overwrite a bricked second chip as some motherboards do. We were going to test this, but we thought we’d better test the cards before breaking them.
HD 6900-series cards should ship with the same output configuration as the HD 6800-series – two DVI (annoyingly, only one of which is dual-link) plus two mini-DisplayPort 1.2 outputs and a HDMI 1.4a. The latter allows 3D, while DisplayPort 1.2 allows daisy-chaining via screens that support this or a Multi Stream Transport (MST) hub. There’s still no news on when we’ll see an MST hub, or how much it’ll cost; we’ve also not heard anything about a HD 6000-series Eyefinity 6 card
ATI has used what it describes as a ‘massive’ vapour chamber cooler for the HD 6900-series, which should help keep down the noise while providing top-notch cooling. Skip to the HD 6970 Thermals
page to see how effective this cooler is.