Let’s take a look at a Radeon HD 4890 with its cooler removed:

The power circuit is considerably revised in comparison with the Radeon HD 4870’s and now uses a 7-phase design (refer to our article called ATI Radeon HD 4890: 1GHz Conquered! for details).

The Radeon HD 4890 has a peak power consumption of 190 watts which is 20 watts higher than that of the Radeon HD 4870. A 550W or higher PSU is recommended for a single Radeon HD 4890. A CrossFireX configuration may require a 700W or higher PSU. Our recent review showed, however, that the power consumption estimates provided by the manufacturers are often overstated.

The key difference of the Radeon HD 4890 over its predecessor Radeon HD 4870 is the new RV790 graphics processor. The GPUs installed on my samples of the cards were manufactured in Taiwan on the 8th and 10th weeks of this year. 

The GPU has not changed functionally. It still incorporates 800 unified shader processors, 40 texture modules, and 16 raster back-ends. The transistor count has grown up by 3 million to 959 million while the die has grown from 256 to 282 sq. mm. The GPU frequency has bee increased from 750 to 850MHz and even to 900MHz for the OC version. Moreover, some brands even turn out Radeon HD 4890 with a core frequency of 950 and even 1000MHz! That’s an impressive progress (a 25% frequency growth) within the same tech process although such cards are going to be rather rare. My cards differ in GPU frequencies: 850MHz for the HIS card and 925MHz for the Diamond (which is 75MHz or 9% above the reference frequency). Each card drops its GPU frequency to 240MHz and voltage from 1.31 to 1.05V in 2D mode.

The cards come with 1024MB of memory in eight GDDR5 chips from Qimonda manufactured on the 46th week of 2008.

The chips are revision A1 and are marked as IDGV1G-05A1F1C-40X. They have an access time of 1.0 nanosecond and a rated frequency of 4000MHz, but the reference memory frequency of the Radeon HD 4890 is 3900MHz (300MHz higher than that of the Radeon HD 4870). The memory bus is 256 bits wide. The HIS card has the same memory frequency as the reference card while the Diamond’s memory frequency is overclocked to 4200MHz (300MHz or 7.7% above the reference card’s).

Here are the full specs of these two products: 

The cooling system of the Radeon HD 4890 has not changed much since the Radeon HD 470 and still consists of an aluminum plate that touches the power components and memory chips, a heatsink with copper base, three heat pipes and aluminum ribs, and a plastic casing with blower.

The only differences in the new card’s cooler is that it now has one 8mm and two 6mm heat pipes (instead of two 8mm pipes) pumping the heat from the copper base to the heatsink ribbing.

I don’t think much about this change because the heatsink, which is the key component of every cooler, is still too small to cool the GPU effectively. On the other hand, you can see in the photo above that the current cooler design does not allow to make the heatsink larger.