The new RV790 chip is a 55nm chip and it looks like we are talking about slightly modified and improved version of the 55nm based RV770 chipset. We already wrote that it has a different packaging and at least one pin difference. The newer chip has better thermals and it will have better idle power mode. As such the Radeon HD 4890 should consume less energy in idle mode but due to its higher clocks, it will probably have higher power consumption in full 3D mode. Their shader units should be a bit more efficient but we'd advise you not to expect big improvements. This is a chipset to get ATI by until it launches the 40nm based performance chip and should be enough to hold the fort until then. - FudZilla

Upcoming Radeon HD 4890 How More Power Efficient

Now the Radeon HD 4890 will come with reference dual slot cooler and visually, it will look almost identical to the Radeon HD 4870 accelerator. The cards will be manufactured by ATI, but partners will at least be able to change the coolers. ASUS is the first confirmed that won't use the plain reference cooler design, and there are a few indications that ASUS and some other partners will come out with factory overclocked BIOS and settings. The new chip, RV790 is more power efficient and it allows better overclocking, and frequencies in excess of 850MHz should be easily possible which is exactly what most are hoping for in the end.

And some people even hope for 1000MHz or higher clocks, through overclocking. These cards will have a tough time beating the GeForce GTX 275 and it definitely lags behind the GeForce GTX285, but the Radeon HD 4890 should at least have a better price to performance ratio.