ATI Radeon HD 4890: The RV790 Unveiled
For the purpose of this article, we got our hands on a couple of Asus-built Radeon HD 4890 cards--one standard reference card and one overclocked edition.
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Asus calls their Radeon HD 4890 cards the EAH4890 (standard reference card) and the EAH4890 TOP (overclocked edition). Before we get to the particulars of each, we wanted to detail the accessory and software bundle Asus offers with the cards. Included with both the EAH4890 and EAH4890 TOP are driver and utility discs, a leather mouse pad, an HD component output dongle, an S-Video to Composite adapter, a CrossFire bridge connector, a dual 4-pin to Molex to 6-pin PCI Express power adapter, and DVI to VGA and HDMI (with audio) adapters. You'll also notice a large "Voltage Tweak" badge emblazoned on the box. Asus is also offering an updated version of their SmartDoctor utility with the cards, which gives users the ability to alter the GPU voltages for extreme overclocking. Cool stuff.
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Physically, the Radeon HD 4890 is similar to the Radeon HD 4870. The Radeon HD 4890 features a dual-slot cooling solution, and requires a pair of PCI Express 6-pin power feeds. Max board power has been increased to 190 W, but idle power should be somewhat lower than the 4870 according to AMD.
Along the top edge of the PCB you can see the dual CrossFire connectors, which allow the cards to be used in 2-, 3-, or 4-way CrossFireX configurations, and the outputs on the 4890 are identical to the 4870--dual Dual-Link DVI outputs and an HDTV output.
Clock speeds on stock reference Radeon HD 4890 cards like the EAH4890 will be 850MHz for the GPU and 975MHz for the GDDR5 RAM (3.9 Gbps effective). At those clocks, cards will offer 1.36 TFLOPS of compute performance, a pixel fillrate of 13.6 Gpixels/s, and 124.8GB/s of memory bandwidth, on a 256-bit memory bus. Overclocked cards like the EAH4890 TOP will also be available from a few of AMD's add-in board partners, which will likely increase GPU and memory clocks to the 900MHz+ and 1000MHz+ plus range. The EAH4890 TOP, for example, has a GPU clock of 900MHz and a memory clock of 1000MHz.
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With the cooler removed, you can get a good look at the RV790 GPU at the heart of the Radeon HD 4890, and the eight Qimonda GDDR5 memory chips surrounding the GPU. The cooler features a large copper heatsink GPU, with heat-pipes linked to secondary aluminum heatsinks. The memory and the GPU both make contact with the cooler, which exhausts hot air from the system through vents in the card's case bracket.
