ATI HD 6990

It's always a sign of great confidence when a dual GPU card is released. ATI did this last month with their Radeon HD6990 which we are reviewing today and shortly after this, Nvidia launched their GTX590. The former houses two HD6970 cores and the latter two GTX580 cores. We have been unable to obtain a GTX590 to review (they are incredibly scarce) so lets start this review by answering a key burning question based on results from other sites - the ATI Radeon HD6990 is faster than the Nvidia GTX590! The reasons for this are due to power constraints and we'll show exactly why during the course of this article. Now we have got that out of the way, we can explore the HD6990 in depth and compare performance with a number of high and mid-range cards.

Since the 5970 was launched last year it has become clear that thermal dissipation is the key limiting factor for any graphics card. The 5970 has two 5870 cores but runs 125MHz slower (200 MHz slower for the RAM) than a single 5870. The 6990 is only 50MHz slower than a 6970 in core speed but a massive 500MHz slower in RAM speed. Even so, the 6990 is rated at a massive 375W TDP which is right at the limits of what a PCI-E slot (75W) and dual 8-pin connectors (150W each) can provide. Furthermore, automated regulatory circuits on the card will throttle back the speed to stay within this thermal envelope and this happens on some benchmarks 

This compromise would be grudgingly accepted by consumers but AMD/ATI have gone much further to satisfy their consumers by including a (not so) secret switch on the card which "overclocks" the card to the full specifications of 6970 speed, i.e. 50MHz faster core and 500MHz faster memory. Doing so disables the thermal protection circuits and the limits go out the window. TDP can shoot up to extreme levels as we will see later. Needless to say, this is done at the risk of the consumer and removing the security sticker over the button invalidates the warranty but is the only way to achieve true CrossFire performance with a single card.

the price od ati hd6990 is approx 699$ or 31000 inr.