|Sapphire Radeon HD 4890 RV790 Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Olin Coles|
|Friday, 03 April 2009|
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Radeon 4890 Closer Look
So what are you expecting the Radeon HD 4890 to look like? If you didn't have high-hopes of a new design, you'll be fine. The reinvented RV770 GPU found in the Radeon HD 4850/4870 video cards is now calling itself the RV790 and lives in the Radeon HD 4890. If you weren't given more details about the new Radeon 4890, the video card could be mistaken for a polished-up 4870; but mistakes aren't allowed at this level so we'll have to put our faith into AMD and presume there's more to it for now. But is there really difference?
The Sapphire Radeon HD 4890 cannot be denied its roots, because when you compare it against the Radeon HD 4870 the outward differences are negligible. ATI originally designed the Radeon HD 4870 with a balanced blend of value and performance, and the HD4890 rebuffs the performance while keeping an eye on value. The third generation 55nm RV790 chip uses the industry's most energy efficient manufacturing process and adds an additional three-million transistors, which allows ATI's latest and greatest single-chip graphics card to achieve top-level gaming performance while being more energy efficient at idle. Featuring the industries only major implementation of GDDR5 video frame buffer memory, the RV790 graphics processor is allowed to operate under stress without the worry of burning-up video RAM.
All Sapphire graphics cards in the HD 4000 series incorporate the latest ATI Avivo HD Technology for enhanced video display and feature a second generation built in UVD (Unified Video decoder) for the hardware accelerated decoding of Blu-ray and HD DVD content for both VC-1 and H.264 CODEC's, as well as *.mpeg files, considerably reducing CPU loading. The dedicated HDMI adaptor connects through the S-Video port and has 7.1 surround sound support and delivers audio and video output on a single cable for direct connection to an HDMI ready display. Unfortunately, there is no support for the up-and-coming DisplayPort interface on the Radeon HD 48xx series.
The ATI Radeon HD 4800 Series GPUs can all upscale video up to 2560x1600 resolution on capable dual-link monitors, which is almost twice the display resolution of 1080p HDTV displays. This bodes well for all Radeon HD 48xx owners wanting more from Blue-ray movies, but this isn't a centerpiece feature of the Radeon HD 4890 we're reviewing for this article.
While I am a huge fan of externally-exhausting VGA coolers such as the one used again on the Radeon HD 4890, I wasn't at all pleased with the exposed electronics that were inherent of the stock cooling package. On the other hand, I am also less enthusiastic about internally exhausting coolers which heat internal hardware, even if they do protect the components. Considering the compromise, it seems that ATI has designed an economical thermal solution which is nearly identical to the one featured on their Radeon HD 4870 series product line.
The cooling unit on the ATI Radeon HD 4890 video card is held tight to the RV790 55nm GPU with the use of a four-corner reinforcing bracket and nine screws. With a die size of 282 mm2, the RV790 GPU offers a greater contact footprint with the cooling unit, compared to the 256 mm2 footprint on the RV770 GPU. The double-height cooler does a very good job of cooling the 4890, but there is still a tremendous amount of heat that builds up on backside of the PCB. If you're an overclocker, there isn't much that can be done to help cool the unit from the reverse side of the circuit board, especially since there are no surface-mounted GDDR5 modules on this side of the video card.
The RV790 operates at 850 MHz by default, and ATI offers top-bin GPUs for factory-overclocked models which run at 900 MHz. Unfortunately, the increase in heat output is directly obvious. At idle, the Sapphire Radeon HD 4890 reference build recorded a warm 57°C, and under load that number raised to 84°C with an ambient room temperature of 18°C. These are the temperatures we experienced on overclocked Radeon HD 4870's a few months back, which brings up the question of how much has really changed.
In our next section we detail our methodology for testing video cards. Following this we offer a cadre of benchmarks to show where the Sapphire Radeon HD 4890 stands against the top-end market of GeForce and Radeon graphics products... so please read on!