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ATI Radeon HD 4855

ATI Radeon HD 4855 Image ATI RV770 Image
The Radeon HD 4855 was a graphics card by ATI, launched in January 2010. Built on the 55 nm process, and based on the RV770 graphics processor, in its RV770 PRO variant, the card supports DirectX 10.1. The RV770 graphics processor is an average sized chip with a die area of 256 mm² and 956 million transistors. Unlike the fully unlocked Radeon HD 4870 Mac Edition, which uses the same GPU but has all 800 shaders enabled, ATI has disabled some shading units on the Radeon HD 4855 to reach the product's target shader count. It features 640 shading units, 32 texture mapping units and 16 ROPs. ATI has placed 512 MB GDDR5 memory on the card, which are connected using a 256-bit memory interface. The GPU is operating at a frequency of 575 MHz, memory is running at 900 MHz.
We recommend the ATI Radeon HD 4855 for gaming with highest details at resolutions up to, and including, 1280x720.
Being a dual-slot card, the ATI Radeon HD 4855 draws power from 1x 6-pin power connectors, with power draw rated at 110 W maximum. Display outputs include: 1x DVI, 1x HDMI, 1x VGA. Radeon HD 4855 is connected to the rest of the system using a PCIe 2.0 x16 interface. The card measures 220 mm in length, and features a dual-slot cooling solution.

Graphics Processor

GPU Name: RV770
GPU Variant: RV770 PRO
Architecture: TeraScale
Process Size: 55 nm
Transistors: 956 million
Die Size: 256 mm²

Graphics Card

Released: Jan 3rd, 2010
Production Status: End-of-life
Bus Interface: PCIe 2.0 x16

Clock Speeds

GPU Clock: 575 MHz
Memory Clock: 900 MHz
3600 MHz effective


Memory Size: 512 MB
Memory Type: GDDR5
Memory Bus: 256 bit
Bandwidth: 115.2 GB/s

Render Config

Shading Units: 640
TMUs: 32
ROPs: 16
Compute Units: 8
Pixel Rate: 9.20 GPixel/s
Texture Rate: 18.40 GTexel/s
Floating-point performance: 736.0 GFLOPS

Board Design

Slot Width: Dual-slot
Length: 8.66 inches
220 mm
TDP: 110 W
Outputs: 1x DVI
1x VGA
Power Connectors: 1x 6-pin

Graphics Features

DirectX: 10.1
OpenGL: 3.3
OpenCL: 1.0
Shader Model: 4.1


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Card Notes

Lantic Exclusive

Rebranded HD 4830 with a HD 4870 PCB

Retail boards based on this design

Name GPU Clock Memory Clock Other Changes
Lantic HD 4855 575 MHz 900 MHz
Lantic HD 4855 1 GB 625 MHz 900 MHz 1024 MB, Dual-slot