NVIDIA's Multiple Clocks

While it has been barely available for a month, the latest generation graphics card from NVIDIA, the GeForce 7800 GTX, has set the pulses of hardware enthusiasts racing with its impressive performance. You would think that despite its availability in retail, not that many people would be playing with it given its considerable price tag. Yet even within such a short period of time, hardware enthusiasts have already uncovered an unexpected aspect of this exciting new card. Namely, they discovered that the GPU frequency increased by around 40MHz whenever they started a 3D application. This subtle boost could only be observed through real-time monitoring of the GPU frequency.

It wasn't too long before someone in the community confronted NVIDIA about this. And the cat is now out of the bag. NVIDIA's Chief Scientist David Kirk has confirmed that there are multiple internal clocks that operate at different frequencies dynamically, depending on the load. While NVIDIA has not yet revealed the full details, the short version of the story is that the chipmaker has incorporated some power-saving techniques acquired from its experience with mobile parts in the design of the GeForce 7800 GTX. We are already well aware of this fact, but what no one realized is that they used this same clock-gating technique to increase frequencies in certain parts of the GPU. Essentially, there is no single clock speed for the GeForce 7800 GTX, as the internal clocks frequencies for different portions of the GPU scale up or down according to the demands on the card.

This previously unknown feature seems to be a trump card that NVIDIA has been unwilling to divulge until this surprise discovery. NVIDIA has promised to work with others in order to clarify the different frequencies and how that affects overclocking. With this information made known, so what does the 430MHz clock speed refer to when entering a 3D API? Well, it's simply a base/primary clock speed that the GPU operates in 3D mode. With this dynamic clock ramping in load situations, NVIDIA is actually giving users a speed boost, albeit without really made known in black and white. Meanwhile, there are questions about the extent of the vendors' knowledge of this hidden feature. After all, what does it really mean when vendors advertise their products as operating at a certain frequency when it has been revealed that the card naturally ramps up to such frequencies during 3D applications? Are they reflecting to this in the adverts? There is certainly potential for marketing mischief here and we've already identified some products that do play around this 'loophole'.

Putting aside such questions for now, we have already seen a pre-overclocked GeForce 7800 GTX from Leadtek and other vendors have introduced their own extreme versions of the GeForce 7800 GTX that offer higher frequencies. Today in our labs, we take a look at a GeForce 7800 GTX from MSI that also features vendor endorsed overclocking. As some of you may be aware, MSI has its own Dynamic Overclocking Technology (D.O.T), a software based utility that allows users to increase the frequencies by fixed intervals. We shall see how useful is that feature later but now, let's take a look at the card and its specifications:

Presenting MSI's version of the GeForce 7800 GTX.