Visiontek ATI Radeon HD4870 512MB GDDR5 PCI Express Video Card Review :: ATI HD4870 Features

06-29-2008 · Category: Hardware - Video Cards

By Ben Sun
  • 55 nanometer process
  • 965 million transistors
  • 800 Stream Processors
  • 750MHz Core Clock Speed
  • 1.8GHz (3.6GHz memory speed)
  • 256-bit memory bus
  • 27.2 Gigatexel Texture fillrate
  • 16.8 Gigapixel Pixel fillrate
  • 115.2GB/second memory bandwidth
  • 512MB memory
  • GDDR5 memory
  • 1.2 TeraFLOPS computing
  • 8x MSAA
  • Up to 24x CFAA
  • 16X AF
  • DirectX 10.1
  • Shader Model 4.1
  • CrossFireX
  • Dynamic Geometry acceleration
  • Game physics processing capability
  • AVIVO HD video and display technology
  • Unified Video Decoder 2 (UVD)
  • HD Video built in HDMI with 7.1 surround sound support on chip HDCP
  • ATI Power Play technology
  • Tessellation Unit

Visiontek ATI Radeon HD4870 512MB GDDR5 PCI Express Video Card Review
Brand NameVisiontek
Part NumberATI Radeon HD4870 512MB PCI Express
Graphics ChipRV770
Core clock750MHz
Shader Clock750MHz
SPs800
Fabrication Process55 nm
Transistors965 Million
Memory clock1.8GHz/3.6GHz
Memory Interface256-bit
Memory bandwidth115.2GB/second
Memory Size512MB
ROPs16
Texture Filtering Units80
Texture Filtering Rate25 Gigatexels/second
HDCP SupportYes
HDMI SupportYes (via adapter)
Connectors2x Dual-Link DVI, TV-Out
RAMDACs400MHz
Bus PCI Express 2.0
Form FactorDual Slot
Power Connectors 2x 6-pin

The Radeon HD4870 is based upon ATI’s RV770XT chip and is the second 7xx series card to hit the market after the Radeon HD4850 launch a short week ago. This is the same chip as the HD4850 with 965 million transistors built on TSMC’s 55 nanometer process. The main differences between the HD4870 and HD4850 are the clock speeds and the memory type. ATI has chosen to go for a smaller chip that can be used easily in double chip configurations ala 4870X2 coming than NVIDIA’s large chip the GT200 which has 1.4 Billion transistors and is much larger.

The HD38xx series was ATI’s first chip to support the DirectX 10.1 standard, an incremental update to the DirectX 10.0 standard that was released with Microsoft’s Vista Operating System. The new API introduced longer Shaders and improvements to the anti-aliasing to Shader Model 4.0. Few games today take advantage of the new API but as the last major update to DirectX until DX 11.0, 10.1 will be used in games as developers want.

The HD48xx series has several improvements including an improved Tessellation Unit. Tessellation allows developers to use fewer triangles to represent more detailed surfaces. The first graphics card with the capability to do Tessellation was the NV1 from NVIDIA that used NURBs (Non Uniform Rational B-splines). The HD4870 and 4850 can do Tessellation better than the HD3xxx series.

ATI is partnering with Intel and their Havok Physics Engine for games. NVIDIA bought Ageia the makers of PhysX, a competing standard. ATI supports open standards. The HD4870 is capable of 1.2 TeraFLOPS of computing power and is the second card after the HD4850 to do 1 TFLOP or more. The 800 Shader Processors are capable of 160 5D operations in a single clock cycle.

The HD4870 is the first graphics card available to use GDDR5 memory. GDDR memory was introduced in graphics cards in 1999 with the launch of the GeForce DDR card from NVIDIA. ATI was the first graphics card company to introduce GDDR3 memory and today are the first to use GDDR5. GDDR5 memory doubles the bandwidth of GDDR3/4 memory by running at near double the clock speed, meaning that a graphics card with GDDR5 would need half the memory bus to achieve the same bandwidth on the same clock speed.

Visiontek decided to clock the card at the default 750MHz clock speed. The HD4870 has a texture fillrate of 27.2 Gigatexels/second and a Pixel fillrate of 16.8Gigapixels/second. ATI says that their card is capable of “Always On 8x MSAA” but as we’ll see in Crysis it depends on the application. The card is a technological marvel when compared to the GTX280 and 260 cards as those are much larger require more power and the die size of the GTX280 is more than twice as big as the 4870.

ATI’s multi-GPU solution is called CrossFireX. To facilitate Crossfire mode on the HD4870, ATI decided to allow up to four HD4870s to be used together improving performance in applications that can use the extra power more cards can deliver. ATI says that they have great scaling on the HD4870 and the card should have the power when enabled to outrun the competition from NVIDIA in the same price range, the GTX280.

Anti-aliasing alleviates jaggies in a computer application such as games. The HD4870 is capable of single-pass 8 sample Multi-Sample Anti-Aliasing. ATI also has a feature called Custom Filter Anti-Aliasing which effectively increases the number of samples being used in improving the image up to 24X. Some, including Scott Wasson from Tech Report and myself don’t like CFAA as it blurs the images in games, but it is an option you can turn off if you don’t like it. ATI’s Unified Video Decoder 2 (UVD) is their second generation video decoding engine that allows the computer to run High Definition Video like Blu-Ray using the software decoder. ATI has always offered media playback in the form of software DVD decoders that outperform the hardware decoders and the UVD2 is an excellent feature of the new card. Several improvements have been made including up-scaling, decoding multiple HD streams at the same time, and dynamic contrast enhancement.