Radeon HD 6870 in DetailUnlike the Radeon HD 5870, the new Radeon HD 6870 is not a huge graphics card. It's not exactly compact either, but for a mid-range card we would say it's about average. The AMD reference card measures 25cm long and weighs roughly 1kg making it 3cm shorter than the Radeon HD 5870.
The GPU has been fabricated using the 40nm process, except it features 454 million less transistors than the Radeon HD 5870's Cypress XT core. This allowed AMD to shrink the die from 334mm2 to 255mm2, making the Radeon HD 6870 more fuel-efficient.
The core is clocked at an impressive 900MHz, 50MHz higher than the Radeon HD 5870, while the GDDR5 memory operates slightly slower at 1050MHz. Pairing that frequency with a 256-bit wide memory bus gives the Radeon HD 6870 134.4GB/s of bandwidth, slightly less than the HD 5870.
The Radeon HD 6870 differs from the older HD 5870 is in its core configuration. The HD 6870 has been downgraded from 1600 SPUs (Stream Processing Units) and 80 TAUs (Texture Address Units) to 1120 SPUs and 56 TAUs, while there are still 32 ROPs. It'll be interesting to see how this impacts the HD 6870, as it has 30% less SPUs and TAUs than the Radeon HD 5870, though again it's made evident this is more of a cut-down mid-range offering based on a refined version of the same technology.
Cooling the HD 6870's Barts XT GPU is a fairly large aluminum heatsink, comprised of 30 fins measuring 11cm long, 6.5cm wide, and 2.5cm tall. Connected to the base of the heatsink are three copper heat pipes that help improve efficiency, and a 75x20mm fan draws air in from the case and pushes it out through the rear expansion slot.
The fan operates very quietly for the most part, partly thanks to the card's impressively low 19W idle consumption. That said, it of course spins up when gaming, as the card consumes up to 151W under load -- 20% less than AMD's numbers for the 5870.
The heatsink and fan are inside a housing that conceals the entire graphics card. AMD adopted this design with the Radeon HD 5870 and it helps protect the product very well; Nvidia does the same with its most prized cards.
To ensure the graphics card gets enough power, AMD has mounted a pair of 6-pin PCI Express power connectors -- identical to what you'd find on the Radeon HD 5870 as well as older Radeon graphics cards such as the 4870 and 4890.
The Radeon HD 6870 supports CrossFire technology with a connector to bridge another 6870. The only other connectors are on the I/O panel and our AMD sample featured two dual DL-DVI connectors along with a single HDMI 1.4a port and two mini-DisplayPort 1.2 sockets.
It is worth noting that all Radeon HD 6870 graphics cards can support a maximum resolution of 2560x1600 on up to three monitors. Additionally, if a multi-stream hub is used with the mini-DisplayPort 1.2 sockets, the card can power up to six monitors.