AMD CrossFire

The CrossFire brand name was retired by AMD in September 2017, however the company continues to develop and support the technology for DirectX 11 applications.

[5] The system required a CrossFire-compliant motherboard with a pair of ATI Radeon PCI Express (PCIe) graphics cards.

Low-end Radeon x1300 and x1600 cards have no "CrossFire Edition" but are enabled via software, with communication forwarded via the standard PCI Express slots on the motherboard.

As many people found a 60 Hz refresh rate with a CRT to strain one's eyes, the practical resolution limit became 1280×1024, which did not push CrossFire enough to justify the cost.

This is similar to X1300 CrossFire, which also uses PCI Express, except that the Xpress 3200 had been built for low-latency and high-speed communication between graphics cards.

[8] While performance was impacted, this move was viewed as an overall improvement in market strategy, because Crossfire Master cards were expensive, in high demand, and largely unavailable at the retail level.

ATI has said that future revisions of the Catalyst driver suite will contain what is required for X1800 dongleless CrossFire, but has not yet mentioned a specific date.

The setup, which, according to internal testing by AMD, will bring at least 3.2x performance increase in several games and applications which required massive graphics capabilities of the computer system, is targeted to the enthusiast market.

Instead, they use XDMA to open a direct channel of communication between the multiple GPUs in a system, operating over the same PCI Express bus which is used by AMD Radeon graphics cards.

Thus, XDMA was selected for greater GPU interconnection bandwidth demands generated by AMD Eyefinity, and more recently by 4K resolution monitors.

Bandwidth of the data channel opened by XDMA is fully dynamic, scaling itself together with the demands of the game being played, as well as adapting to advanced user settings such as vertical synchronization (vsync).

[21] GPUOpen offers some MIT-licensed source-code for DirectGMA applications with multiple AMD GPUs in conjunction with Direct3D 11, OpenGL and OpenCL: https://github.com/GPUOpen-LibrariesAndSDKs/DirectGMA_P2P There is also a "hybrid" mode of CrossFireX that combines on-board graphics using the AMD northbridge architecture with select graphic cards,[22] for increased performance.

[26][27] As of March 2012, it appears that this is now called "AMD Radeon Dual Graphics" and means using A-series APUs together with video cards.

A CrossFireX connection on a graphics card
Top view
Bottom view of a CrossFireX bridge interconnect
AMD CrossFireX and some R700 GPUs, in Radeon HD 4000 series
XDMA might be similar the AMD DirectGMA (Direct Graphics Memory Access) to be found on AMD FirePro , and Radeon Pro branded product lines.