Before it was AMD, ATI had a bit of a trick on some of its GPUs. You could unlock the deactivated execution units of graphics processors, such as stream processors and texture units and make them more powerful.
In one case it was possible to upscale cheaper chips until they matched the Radeon 9700 Pro.
It also seemed that the 128 disabled stream processors of AMD Radeon HD 6950 could be easily re-activated by flashing-in a BIOS of the more expensive Radeon HD 6970, which had 1536 stream processors.
But according to Xbit Labs, it looks like that has come to an end with the Radeon 6970 “Barts LE”. AMD has confirmed that it cannot be transformed into more powerful 6870 (1120 SPs) or 6850 (960 SPs) as the non-operating units are fused off. They have been physically disabled to prevent any software tinkering,
To make it up to overclockers, the Radeon HD 6790 comes with extra cooling and the thought is that punters will be able to speed up the card by overclocking it significantly.
The downside is that overclocking voids the card’s warranty. However some card makers are expected to be jacking up the clock-speed so that their product looks a bit different from the rest.
AMD plans to keep the Radeon HD 6790 on the shelves for a while and insists it is not a temporary chip which is designed to plug a gap in the market.