MSI R4870 T21G ATI Radeon HD 4870 1GB Review :: MSI Radeon R4870 T21G HD 4870 1GB Features

11-12-2008 · Category: Hardware - Video Cards

By Ben Sun
  • 1024MB of GDDR5 memory
  • 256-bit memory interface
  • 900MHz memory clock
  • 115.2GB/second memory bandwidth
  • 750MHz Core Clock speed
  • DirectX 10.1
  • 756 Million transistors
  • 800 SPs
  • 32 ROPs
  • 55 nanometer manufacturing process


MSI R4870 T21G ATI Radeon HD 4870 1GB Review

Brand Name MSI
Part Number R4870 T21G
Graphics Chip RV770XT
Core clock 780
Shader Clock 780
SPs 900
Fabrication Process 55 nanometer
Transistors 956 million
Memory clock 3.6GHz effective
Memory Interface 256-bit
Memory bandwidth 115.2GB/second
Memory Size 1GB
ROPs 16
Texture Filtering Units 32
Texture Filtering Rate 20 Gigatexels/second
HDCP Support Yes
HDMI Support Yes (via adapter)
Connectors 2x Dual-Link DVI, TV-Out
RAMDACs 400MHz
Bus PCI Express 2.0
Form Factor Dual Slot
Power Connectors 2x6-pin

The HD 4870 is based upon ATI's RV770XT chip which was launched back in August of this year. The RV770XT has 956 million transistors and is built on TSMC's 55 nanometer process, offering higher performance and lower power consumption compared to earlier video cards like the HD 2900XT which was built on the 65 nanometer process and drew a lot of power.

The HD 4870 has 800 Stream Processors which is not exactly the same as NVIDIA's 256 SPs on the GeForce GTX 280. The HD 4870 has 10 SIMD cores each with 16 SP clusters capable of doing a single 5D operation in single clock cycle. This adds up to 800 Stream Processors in ATI's documentation. The Radeon HD 4870 has 40 texture units that more than double the number of texture units on the previous generation HD 3870. The number of render back ends (ROPs) is the same as the HD 3870 but does nearly double the output of it when AA and 64-bit color is used.

ATI has really been pushing the DirectX 10.1 standard as the next big thing in graphics. Unfortunately for them they really haven't had much luck in getting DirectX 10.1 games out as they don't develop games. As we move forward, the graphics API will change to DirectX 11, necessitating support for DirectX 10.1 due to the fact that the later revisions of DirectX require backwards compatibility with older versions meaning that the companies that support the features will get rewarded with certification and those who don't won't.

MSI's card is overclocked from the standard HD 4870. The standard card has a clock speed of 750MHz. The MSI card has a core clock speed of 780MHz, a 30MHz improvement over the default clocked cards. The memory clock is the same as on the reference clocked card which is 900MHz. Due to the nature of GDDR5 memory the memory bandwidth is effectively doubled over that of GDDR3 memory. The HD 4870 has a 256-bit memory bus meaning this card has an effective memory bandwidth of 115.2GB/second.

The advent of High Definition Videos and HDTVs has caused both NVIDIA and ATI to release hardware on their new video cards to decode/encode the HD media. Blu-Ray discs have won the HD optical media war with HD-DVD and the HD 4870 is ready for it. The Universal Video Decoder 2nd generation built into the HD 4870 can run two video streams simultaneously. This allows the end-user to watch the movie and run the special features of the BRD simultaneously in Picture in Picture (PIP) mode. The other feature that the UVD2 brought to the table with the HD 4xxx series is the ability to dynamically adjust the contrast of a video.