AMD CrossFire
AMD CrossFire (formerly called AMD CrossFireX , in the initial phase ATI Multi-Rendering ) is a process by the company AMD to increase graphics performance by using several graphics cards at the same time in a PCI Express system. The limit of cards that can currently use this technology at the same time is four.
The same procedure is used when two GPUs are on the same card or one GPU is on the motherboard (for example in the chipset) and another on a plug-in card ("Radeon Dual Graphics").
functionality
First of all, a special monitor cable (DVI-Y dongle) was required, via which both graphics cards are connected externally to the DVI connection, so that data can be exchanged between the graphics cards. Here a so-called master card (recognizable by the name "Crossfire Edition") is required, which is combined with a slave card (common version). A chip on the master card regulates the data exchange between the two graphics cards in order to output an image on the monitor.
At the end of 2006, with the introduction of the Radeon X1650 XT and Radeon X1950 Pro , the internal CrossFire, referred to as "native" by AMD, was presented. Two identical graphics cards are connected with a CrossFire bridge cable via two connections. The monitor is connected to one of the two graphics cards. Exceptions are some cheap or standard graphics cards with less performance than high-performance graphics cards: Here communication between the two graphics cards takes place exclusively via the PCI Express bus, similar to MultiChrome from S3 Graphics or the less powerful SLI variant from Nvidia .
At the end of 2007, CrossFireX was introduced with AMD's Spider platform. With CrossFireX it is now possible to operate up to four GPUs at the same time. The difference to the SLI from NVIDIA is that with CrossFire data can generally be exchanged bidirectionally .
At the end of 2013, AMD introduced the so-called XDMA technology for the first time with the presentation of the graphics cards with the code name Hawaii . "XDMA" (X = CrossFire, DMA = Direct Memory Access) should make it possible to dispense with the additional bridges between the graphics cards even with high-end graphics cards and to let the communication between the GPUs run via PCIe.
Differences between the CrossFire generations
| designation | Publication date | Max. Number of GPUs | Master card required | Crossfire bridge cables | annotation |
|---|---|---|---|---|---|
| CrossFire | 09/26/2005 | 2 | Partially | Partially | |
| CrossFireX CrossFire ™ |
11/19/2007 | 4th | No | Partially | Works with graphics cards from the Radeon HD2000 series with two to four cards of the same series ( see below ). |
| XDMA | October 24, 2013 | 4th | No | No | from R290 series |
Micro-stuttering
Both CrossFire and SLI primarily use alternate frame rendering . At the moment, the phenomenon often occurs that every second frame is calculated more slowly than the previous one. So-called "micro stutters" occur. This leads to an uneven flow of the game, which is particularly annoying at relatively low frame rates. As a result of this fact, graphics cards in CrossFire mode need a significantly higher average frame rate than a single graphics card in the games in question, in order to guarantee a relatively smooth display for the eye. This problem also occurs with dual-GPU graphics cards as well as with "dual graphics" systems, since both also use crossfire technology. The fact that the higher average frames per second in benchmarks in Crossfire mode does not provide better playability means that in detailed test reports, CrossfireX in particular with graphics cards up to the mainstream is discouraged and a single card is recommended.
In August 2013, AMD implemented the so-called frame pacing in the Catalyst 13.8 Beta 1 driver. The frame, which is calculated very quickly, is slightly delayed when it is output to the screen by means of an intermediate buffer. The frame rates become more even again and the maximum latencies between two consecutive frames are reduced, as the waiting time for the following, slowly calculated frame is reduced. With this workaround, there are significantly fewer micro stutters and the games become more playable, even if the average FPS number drops slightly. The improvements are clearly noticeable almost everywhere and the result is just as good as with SLI systems, in which this technology has been used for a long time. The micro-stuttering has not completely disappeared, but the game flow is now comparable for the first time with that of single GPU systems. AMD has announced the first WHQL driver with frame pacing and other improvements for 2014. Currently there are the restrictions that frame pacing can only be used with GPUs with GCN architecture (from HD7000 series) and only up to a resolution of 2,560 × 1,600. Higher resolutions are currently only compatible with the Radeon R9 290 and R9 290X with the frame pacing driver. For DirectX 9c and OpenGL games there is also no support for frame pacing yet.
Operating modes
Four different operating modes are offered:
- SuperTiling : Standard for Direct3D applications.
- Scissor: (also known as Split Frame Rendering (SFR) with load balancing). Standard for OpenGL applications.
- Alternate Frame Rendering (AFR): Highest results in benchmarks, but problems with micro-stuttering.
- SuperAA : A quality mode in which both graphics cards calculate the same frame with different FSAA patterns. This enables larger FSAA factors.
Graphics cards with CrossFire support
The mutual compatibility is clearly shown on a corresponding website at AMD.
| Graphics card series | CrossFire generation |
Master card | Crossfire bridge cables |
Remarks | |
|---|---|---|---|---|---|
| Radeon X800 series | CrossFire | Yes | - | ||
| Radeon X850 series | CrossFire | Yes | - | ||
| ATI Radeon X1000 series | CrossFire | Partially | Partially | The X1300, X1500 series and X1600 Pro / XT do not require a master card or a bridge cable. The X1650 XT, X1950 GT and X1950 Pro only require a bridge cable. | |
| ATI Radeon HD 2000 series | CrossFire | - | Yes | ||
| ATI Radeon HD 3000 series | CrossFireX | - | Yes | ||
| ATI Radeon HD 4000 series | CrossFireX | - | Partially | The HD-4300, HD-4500 and HD-4600 series do not require a Crossfire bridge cable (exception: 2-4x HD 4670) | |
| ATI Radeon HD 5000 series | CrossFireX | - | Partially | The HD-5400, HD-5500 and HD-5600 series do not require a Crossfire bridge cable (exception: 2-4x HD 5670) | |
| AMD Radeon HD 6000 series | CrossFireX | - | Yes | ||
| AMD Radeon HD 7000 series | CrossFireX | - | Yes | ||
| AMD Radeon R200 series | CrossFireX | - | Partially | Thanks to a new process, the R9 290 and R9 290X no longer require a bridge cable |
- ↑ These ATI graphics cards can only handle CrossFire with an external connection and the use of a master card (Crossfire Edition). A master card and a slave card are required, whereby a more powerful slave card must be based on the performance of the master card. The CrossFire-Edition master cards have “CF” as a suffix (e.g. X1950CF: 'Master card', X1950XT: 'Slave card'). The X1950CF sometimes has a GPU clock that is 10 MHz lower.
Dual GPU graphics cards
All previous dual-GPU graphics cards under the brand name ATI are based on Crossfire technology. Initially, some ATI partners - such as Sapphire or GeCube - produced dual GPU graphics cards on their own, such as the X1950 Pro Gemini or the X1650 XT Gemini. AMD later took over the development itself and presented a reference design to all partners. The two GPUs are connected to a PCIe switch on the card and run in Crossfire mode. Up to the HD3870 X2 the PCIe switch supported PCIe of the first generation, from the HD48xx X2 the PCIe switch supports PCIe 2.0 and thus offers more bandwidth for communication between the two GPUs.
Hybrid CrossFireX
With Hybrid CrossFireX it is possible to connect an AMD chipset with an integrated graphics processor (from the AMD 7 chipset series ) and a low-end graphics card HD 3450 or HD 3470 (as of April 2011) to increase graphics performance.
The monitor can either be connected to the main board or the graphics card for image output . When the monitor is connected to the motherboard, the graphics card has no function in 2D applications, but it is not switched off. If the monitor is connected to the graphics card, only the dedicated graphics card is responsible for the image output in 2D mode; the IGP is completely switched off here. In both cases, the IGP and dedicated graphics card are interconnected to increase performance if the Catalyst driver provides CrossFireX support for the respective 3D application. For 3D applications without CrossFireX driver support, it is recommended to connect the monitor to the discrete graphics card, since the integrated GPU of the chipset is less powerful than a hybrid CrossFireX-capable graphics card.
In hybrid crossfire mode, both the GPU integrated on the motherboard and the discrete graphics card render their images independently of each other ( alternate frame rendering ). With the release of the Catalyst software suite 8.8, both Windows XP and Vista are supported.
With " Hybrid-SLI " Nvidia offers a function similar to Hybrid-CrossFireX under the name GeForce Boost .
A feature similar to Nvidia's “ HybridPower ”, which can deactivate the discrete graphics card as required, is only offered by AMD for notebook chipsets under the name PowerXPress . PowerXpress is currently (as of June 2008) only supported under Windows Vista.
Web links
Individual evidence
- ↑ a b sites.amd.com: AMD CrossFireX ™ ( Memento of the original from September 3, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b ComputerBase: AMD Radeon R9 290X - CrossFire and Turbo , launch article from October 24, 2013
- ↑ heise online : ATI releases CrossFire technology for coupling two graphics cards , article from September 26, 2005
- ↑ CrossFireX was renamed from AMD to CrossFire: What is the difference between AMD CrossFire ™, AMD CrossFireX, AMD Dual Graphics and AMD Hybrid CrossFire?
- ↑ Planet3dnow: AMD presents "Spider", the first complete PC platform , press release of November 19, 2007
- ↑ AMD CrossFire FAQ: What are the system requirements for AMD CrossFire ™?
- ↑ ComputerBase : The Multi-GPU Problem: Mikroruckler Computerbase, August 12, 2008, accessed on February 16, 2011.
- ↑ ComputerBase: The problem "micro stuttering" Computerbase, January 24, 2011, accessed on February 16, 2011.
- ↑ Computer base: “Microruckler” in “Dual Graphics” mode with a so-called “APU” computer base, June 30, 2011, accessed on August 6, 2011.
- ↑ Tom hardware: Conclusion? Then prefer a single ticket. Tomshardware, July 19, 2011, accessed August 6, 2011.
- ↑ ComputerBase: AMD versus micro stuttering , August 1, 2013.
- ↑ ComputerBase: The Multi-GPU-Duel , December 17, 2013.
- ↑ Overview of the mutual CrossFire compatibility at AMD
- ↑ Heise: Hybrid Crossfire
- ↑ Allround-pc.com: Test of a hybrid crossfire system
- ↑ ComputerBase: Explanations on Hybrid Crossfire
- ^ ATI Catalyst Release Notes. Retrieved January 1, 2014 .
- ↑ Heise: Notebook graphics: The new flexibility ( Memento from June 8, 2008 in the Internet Archive )
