CrossFire, TrueAudio and Eyefinity

A New CrossFire, with Needed Fixes

CrossFire has caused a lot of problems for AMD in recent months.  It caused a lot of problems for me as well.  But AMD continues to make strides in correcting the frame pacing issues associated with CrossFire configurations and the new R9 290X moves the bar forward.

Without the CrossFire bridge connector on the 290X, all of the CrossFire communication and data transfer occurs over the PCI Express bus that connects the cards to the entire system.  AMD claims that this new XDMA interface was designed for Eyefinity and UltraHD resolutions (which were the subject of our most recent article on the subject).  By accessing the memory of the GPU through PCIe AMD claims that it can alleviate the bandwidth and sync issues that were causing problems with Eyefinity and tiled 4K displays. 

Even better, this updated version of CrossFire is said to compatible with the frame pacing updates to the Catalyst driver to improve multi-GPU performance experiences for end users. 

Here's the secret – I've already tested CrossFire + 4K and found that indeed AMD has improved the technology drastically with the R9 290X!!  Check out that separate preview article for information on CrossFire and 4K performance!

AMD TrueAudio Technology

AMD has been pretty good with audio on their graphics cards for some time.  The HD 2900 XT had a built-in audio processor that did not need a cable passthrough as the competition did.  They were also among the first to offer full 7.1 support for high bitrate audio formats.  They were the card of choice for those bitstreaming HD audio streams to their high end AV equipment.  AMD is taking a big step forward with audio in this generation of products.

AMD’s TrueAudio technology is reserved for the R9 290 series and the R7 260X.  It is also present in the HD 7790, but we are unsure if that functionality will ever be exposed in drivers.  Hardware audio has taken some severe hits through the years, primarily with the death of Aureal at the hands of Creative and the move of the audio stack to software/OS control from Windows Vista onward.

Aureal had a vision of what was essentially raytracing for audio sources.  This is a bit easier and less compute intensive than light raytracing, but a lot of the characteristics are the same.  There is a source in space, it traces a path where the sound goes, and that sound can be reflected, obscured, or absorbed.  Creative took a different direction with EAX in that they did not computer a lot of these paths, and in later versions they finally did some occlusion and other effects.  Creative’s vision for audio was substantially more conservative than what Aureal was trying to accomplish.  Hardware based audio also took a hit when Vista took to market, as it took a lot of the hardware accelerated features out of the hands of the sound chip people and inserted it into their own software stack in the OS.  While some functionality was retained through OpenAL, it was simply not the same.

AMD is reviving hardware accelerated audio, but in a way that is outside of the OS audio software stack.  It works much closer to the application to enable hardware accelerated features and then delivers the output to the OS software stack to be played through whatever playback devices are present.  This takes the work out of the OS’s hands, as well as that of external devices that are only emulating 3D effects (like USB based headphones).  The hope here is that AMD pushes programmable sound just as shaders have pushed 3D graphics.

The basis of TrueAudio is the integration of multiple Tensilica HiFi EP DSP cores into the GPU.  These are dedicated DSPs that can share memory resources with the frame buffer of the card, so they do not require extensive amounts of cache and memory to do the work assigned to them.  The abilities and performance of these DSPs should allow for the hardware acceleration of up to 120 audio streams in realtime.

TrueAudio is designed to work with several audio middleware applications which will provide the effects needed to accurately render a scene in sound.  McDSP and GenAudio are two early examples of this middleware that will work with TrueAudio, and potentially more are on the horizon.  The only real downside here is that the TrueAudio API is limited to AMD products.  Support will be a ways in coming, but if it takes off it will signal the rebirth of spatially accurate audio in applications which can leverage such scenarios.

AMD Eyefinity Changes

Along with the display output change comes an update to Eyefinity.  Gone is the requirement that one of your monitors (in a three display setup) be connected via DisplayPort and instead AMD is going to a solution that mirrors what NVIDIA current supports in its Surround technology.  Users of the R9 cards will be able to connect monitors to any output on the card and have the capability to enable Eyefinity.  DVI + DVI + HDMI?  No problem this time around.

This is enabled thanks to a slight rework of the display timing on the cards themselves.  Because two display controllers now share a timing generator you can now support Eyefinity without requiring any kind of DisplayPort adapter on legacy displays.  This works with single link and dual link port configurations as well.

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