• 2 x 956 million transistors
• 2x 800 Shader Processors
• 2 x256-bit memory interface
• PCI Express 2.0
• PCI Express 2.0 interconnect
• 8-pin and 6-pin power
• DirectX 10.1
• OpenGL 2.0
• 55 nanometer process
• CrossfireX
• ATI PowerPlay technology
• Game Physics processing
• Core Clock 750MHz
• Memory Clock 3600MHz
• Memory bandwidth 230GB
• 2GB GDDR5
• HDMI function via dongle
• Dynamic Geometry acceleration
• Avivo HD

Brand Name	Palit
EVGA Part Number	HD 4870 X2
Graphics Chip	R700
Core clock	750MHz
Shader Clock	750MHz
SPs	800
Fabrication Process	55 nm
Transistors	956 Million
Memory cloick	3.6GHz effective
Memory Interface	256-bit X2
Memory bandwidth	230 GB/second
Memory Size	2048MB
ROPs	32
Texture Filtering Units	64
Texture Filtering Rate	40.6 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	2x 6-pin

ATI is at the forefront of process technology in video cards. The HD 4870 X2 is based upon TSMC’s second generation 55 nanometer process. The R700 card has two RV770 Pro chips which each have 956 million transistors or a total of 1.912 Billion transistors total on the HD 4870 X2. Each of the RV770 chips on the HD 4870 X2 has 800 Stream Processors, broke down into 160 clusters each capable of a single clock 5D operation hence 800 total.

The HD 4870 X2 is the first video card to use 2GB of memory as standard on a single card except for workstation cards and the odd video card like the Power Color PCS HD4850 which ATI was the first video card manufacturer to fully support the Microsoft DirectX 10.1 API. This is mostly a cosmetic improvement to DirectX 10.0 with improved features for Anti-Aliasing, adds support for parallel cube mapping and 32-bit operations throughout the pipeline. NVIDIA states that DirectX 10.1 isn’t that important but ATI is pushing it as all future versions of DirectX will require support for these features as well.

The memory bus interface on the HD 4870 X2 is extremely interesting in that it has two banks of 256-bit GDDR5 memory. Each bank serves one of the HD 4870 chips and operates at a frequency of 900MHz. Due to the nature of GDDR5 memory, the speed is effectively double that of GDDR3 memory, meaning that the card is clocked at 3.6GHz effective memory. Each chip therefore has a memory bandwidth of 115.2GB/second or 230GB/second total on the HD 4870 X2.

ATI’s CrossfireX is their multi-GPU solution that is supported by their motherboards and Intel motherboards with more than one PCI Express x16 slot. Crossfire’s early implementations required a dongle that hung precariously on the IO of the video card in the X1900XTX cards. ATI later released cards with bridges similar to the one NVIDIA uses for SLI, NVIDIA’s competing standard for Multi-GPU solutions.

As the HD 4870 X2 is basically two HD 4870 cards, a bridge chip is necessary to let them work together. ATI uses their second generation PCI Express Bridge that has a bandwith of 5GB/second to each HD4870 X 2 and 5GB/second to the motherboard. This is effectively 21.8GB/second of bandwidth 3x that of the first generation PCI Express Bridge they used on the HD 3870 X2 cards. ATI has partnered with Intel’s Havok Physics team to support the Havok Physics game engine. Physics in games has been normally controlled by the CPU but with the advent of Ageia PhysX and Intel’s Havok engine, physics has been increasingly moved to the GPU. The HD 4870 X2 is capable of 2.4 TeraFLOPS of computing power and can make good use of that power by using it on game physics. ATI has had a GPGPU client that uses the computing power of graphics cards to solve complex mathematical problems. Here’s a chart showing current pricing and information on the various cards of the latest generation: