Sapphire Toxic Radeon HD 4870 1GB GDDR5 Review :: Features

• 780MHz core clock speed
• 1GHz memory speed 4GHz effective
• PCI Express 2.0 x16 bus interface
• 1024MB GDDR5 memory
• 256-bit GDDR5 memory interface
• Dual-Slot Active cooler
• HDMI compliant via dongle
• 7.1 Audio Channel Support
• Microsoft DirectX 10.1 support
• Shader Model 4.1 support
• 24x custom filter anti-aliasing and high performance anisotropic filtering
• ATI CrossfireX
• Dynamic geometry acceleration
• Game physics processing capability
• ATI AVIVO HD
• ATI PowerPlay

Brand Name	Sapphire
Part Number	TOXIC HD 4870 1G GDDR5 PCI-E
Graphics Chip	RV 770 Pro
Core clock	780MHz
Shader Clock	780MHz
SPs	800
Fabrication Process	55nm
Transistors	956 Million
Memory clock	4.0GHz effective
Memory bus	256-bit
Memory bandwidth	128GB/second
Memory Size	1024MB
ROPs	16
Texture Filtering Units	40
Texture Filtering Rate	32.4Gigatexels/second
HDCP Support	Yes
HDMI Support	Yes
Connectors	Dual Link DVI, HDMI, VGA,
RAMDACs	400MHz
Bus PCI Express	2.0
Form Factor	ATX
Power Connectors	2x 6-pin power

The Radeon HD 4870 is based upon ATI's RV770 Pro chip which was launched last year. This chip had 956 million transistors and was manufactured on a 55nm process. The die size on the RV770 Pro chip is a mere 256mm2 compared to the 576mm2 on the competing GeForce GTX260. The die size difference means more chips can be manufactured on the same wafer, presumably for a lesser price.

The Radeon HD 4870 has 800 Stream Processors. This is split up into 10 SIMD cores. Each SIMD core has 16 Stream Processors that can each do five instructions at the same time or a 5D instruction. The Radeon HD 4870 supports GDDR5 memory which effectively doubles the memory bandwidth compared to GDDR3 memory. Sapphire clocks their memory at 1GHz, effectively giving this card 128GB of memory bandwidth.

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ATI cards have supported DirectX 10.1 since the launch of the Radeon HD 3870 in 2007. NVIDIA has only supported DirectX 10.0 until their recent launch of the GT210 and GT220 video cards for the OEM market and the GTS250M which all support DirectX 10.1. One thing to note is that these chips are not on the enthusiast side of things with 16 and 48 SPs compared to NVIDIA's GTX 285 which has 240 SPs. It should be interesting to see what NVIDIA has in store for the rest of the year as well as ATI.

One of Sapphire's big pushes with their Toxic series is their Vapor-X technology. Vapor-X operates much like a heat pipe. The graphics chip heats the vaporization Wicks, and the water inside the Vapor chamber vaporizes and the vapor moves to the condensing wick turning back to water. The liquid is then absorbed by the Transportation Wick by capillary action and moves back towards the Vaporization Wick starting the process all over again.

Multiple graphics cards on the same gaming system have been around for years, made famous by the 3DFX Voodoo 2 SLI, multi-card gaming has gone a new direction with the demise of that company in 2000. NVIDIA released their version of SLI in 2004 with the nForce 4 SLI. ATI followed suit quickly with the launch of the X1900XTX cards. Today every ATI card with a Crossfire bridge has the ability to Crossfire with other cards. Up to four ATI cards can work together improving game performance.