The Asus EAH4890 TOP videocard uses the PCI Express x16 2.0 bus interface and features a single Radeon HD 4890 GPU, code named 'RV790.' The RV790 graphics chip is built on a 55nm process and packs roughly 956 million transistors into a 282mm square GPU die. The shift in architecture from the R600 series of GPUs means that RV790 runs cooler and consumes generally less power, which in turn lets AMD's engineers turn up the overall performance. It also means that there are now 800 stream processors on board (up from 320 in the Radeon HD 3870), and 40 texture units (up from 16). DirectX 10.1, Shader Model 4.1, OpenGL 3.0 support is standard.

The default clock speeds for the ATI RV790 are 850MHz GPU, 975MHz memory quad-pumped.

When calculating the speed of the Radeon HD 4890's memory it's important to remember the actual effective speed is 3.9GHz because it is using GDDR5 memory. The AMD Radeon 48xx series are the only videocards to take advantage of GDDR5, a memory standard that allows for quad-pumping. This means the the base 975MHz clock of the memory is actually signalling four times per clock cycle, for an effective speed of 3900MHz (975 x 4). By comparison even the latest GT200 GPU NVIDIA cards are still using older GDDR3 memory, which can only be dual-pumped. NVIDIA compensates for this by using wider 448 or 512 bit memory interfaces.

The Radeon HD 4890 supports audio through a DVI-to-HDMI adapter, along with H.264, MPEG-2 and VC-1 hardware decoding, as well as HDCP compliance. The HDMI output carries 7.1 channel audio, making it a great alternative if you're gaming on an HDTV or simply want to output movies from a Blu-ray DVD drive to your big screen. These technologies are collectively wrapped up in ATI's Avivo HD video and display platform which makes use of the aforementioned Unified Video Decoder 2.

ATI CrossfireX Multi-Videocard Teaming

While we didn't get a chance to test this ASUS EAH 4890 TOP HTDI/1GD5/A in Crossfire, AMD's multi-GPU technology does deserve attention.

AMD Crossfire has steadily improved in performance and compatibility since it was first introduced with the Radeon x850 GPU. While older Crossfire versions required a tricky master-slave card scheme in order to function properly, the current version of Crossfire X is much more user friendly, and supported on most of Intel and AMD motherboard chipsets. CrossfireX can be scaled across as many four GPUs, although quad-Crossfire adopters might want to be warned this rarely if ever gives linear performance scaling, as we've demonstrated in previous reviews.

Heat and Noise Observations

AMD lists the maximum board power draw for the ATI RV790 based videocard at 190W. Asus has radically re-designed the cooler for the EAH4890 TOP, and under testing PCSTATS has found that it's improved significantly from the stock cooler. Overall temperatures were lower under heavy load, remaining cool to the touch at moderate fan speeds. The fans themselves were also noticeably quieter, although at full speeds they can be still heard while inside a system chassis.

The Asus EAH4890 TOP can be connected to additional Radeon 48XX videocards using the on-board Crossfire connectors

Let's see if Asus new electrical system has changed the EAH 4890 TOP's power performance...