Product: ATI Radeon HD5970
Company: AMD
Authour: James Prior
Editor: Charles Oliver
Date: November 18th, 2009
HD5970 Card Architecture & Overclocking
HD5970 Review - Page 2

Part of the Evergreen family, code name Hemlock features dual Cypress GPUs. They are specially screened RV870XT ASICs tested to work at HD5870 speeds, and undervolted and downclocked for use in the Hemlock, aka HD5970 card.

Cypress Core Architecture
Cypress Core Architecture

AMD recognizes there are Ultimate PC Enthusiasts out there, for whom wringing the last piece of power and performance out of a part is a valuable aspect of their hobby for Ultra High End PCs. To address these consumers, AMD designed and specified the HD5970 for unlocked performance - overclocking. Taking the best RV870XT ASICs was the first step, with the full complement of 20 SIMD units fully operational at 850MHz speeds. Specifying 5Gbps GDDR5 was the second step. Finally, highest quality voltage regulators and solid Japanese capacitors were used for ensuring ripple free rock steady power to the board components.

Hemlock Architecture
Hemlock Architecture

The minimum requirements for this card are 25A from the system - delivered by the motherboard and dual PCIe power connectors (one 6pin, one 8pin). Most 650W power supplies, suitably equipped with one 75W 6pin and one 150W 8pin PCIe power connector, will be capable of powering the world's fastest GPU; AMD recommends a name brand 750W supply to make the most of it, and 850W with two 6pin and two 8pin for CrossfireX.

These design decisions were subject to much debate inside AMD over the last few months, and about two months ago it was decided to offer a PCIe power specification compliant specification card, rather than an out of the box maximum performance (and power) model. This approach dictates the 725MHz engine clock and 1GHz (4Gbps) memory clocks, to fit the power profile that AMD wanted. The flip side to the superior specification for overclocking means that at the standard clock settings less voltage is needed.

Unlocked Overclocking

Similar to Black Edition CPUs, AMD has raised the roof on the Overdrive clock limits. Rather than the ~10% headroom normally found, the HD5970 receives a whopping ~30% engine clock headroom and ~50% memory clock capability - 1GHz core and 6Gbps limits. Given the inherent over specification of the core and memory, it would be surprising to find Hemlock samples that couldn't hit HD5870 CrossfireX performance levels, using bumped voltages. Another first for Hemlock is AMD encouraging AIBs to include over volt utilities in the box with the HD5970, giving more room for overclocking potential.

Designed for Overclocking
Designed for Overclocking

To cope with this unlocked potential, AMD included a vapor chamber fitted with aluminum fins, capable of 400W dissipation. The reference design also removes the 4th display output normally seen on the rear of the Evergreen GPU's. This full slot output combined with the advanced PowerPlay features means a quiet, cool, efficient desktop experience with Ultimate GPU performance only a shortcut away. Using an S1-like power state, the second GPU is disabled at the desktop, whilst still allowing the primary GPU to adjust to higher clock speeds for Video playback and other 2D GPU tasks. Here the HD5970 delivers a class leading idle power reading of just 42W, slightly less than two Cypress cards.

Greater than stock performance
Greater than stock performance

Similar to AMD's Black edition CPUs, operation outside of specification is not guaranteed or warranted; so if you dump 1.4v through the core @ 1.2GHz, don't come crying; it's dead, Jim.

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