Detailing Richlandís Dual Graphics & GCN Compatibility
The Richland APU and AMDís Graphics Core Next architecture should be two mutually exclusive items which were never meant to be conjoined. With the latest APU refresh using an older Northern Islands design for its graphics processing stages, GCN was effectively off the table until Kaveriís arrival sometime later this year. But GCN is nonetheless entering this equation in a roundabout way.
In our recent preview of the new Richland mobile APUs, it was mentioned that AMD had once again integrated support for Dual Graphics setups. Dual Graphics essentially gives OEMs the ability to pair up an accelerated processing unit with a secondary discrete graphics chip in order to increase performance by a substantial amount. Both Trinity and Llano featured the technology quite prominently and the benefits were impressive in some cases. However, this time around, AMD has made things a bit more interesting.
While Trinityís use of the Northern Islands VLIW4 architecture represented a dramatic step forward from Llanoís Redwood-based ďSumoĒ design, some were expecting this yearís APUs to feature AMDís latest GCN cores. That hasnít happened yet since Richland uses the same layout as its predecessor, though with faster clock speeds and higher performance numbers.
Richland may feature GPU technology which was at its pinnacle two years ago but AMD claimed it would be compatible with Sea Islands discrete cards when used in a Dual Graphics configuration. Conventional wisdom pointed to this being impossible, a simple misstatement by some over-eager media contact or a case of mistaken identity.
Our original hypothesis actually focused on the possibility that some lower-end, as yet unannounced HD 8000M graphics processors were simply rebranded Northern Islands parts. This would of course explain how AMD overcame a litany of potential conflicts but as they say: the truth is often stranger than fiction.
Weíve since learned that Richland APUs are indeed fully compatible with the 28nm Graphics Core Next products within the HD 8000M (code named Solar System) lineup when used in Dual Graphics mode. Even though mixed Crossfire with identical architectures has been around for a while, this is the first time graphics cores from different architectural generations are able to work in concert with one another in an effort to boost framerates.
Compatibility is quite extensive with the new A10 and A8 APUs reaping substantial benefits when paired up with certain HD 87xx and HD 85xx discrete cores. These GPUs all use the new Mars XT or Mars Pro GPU and feature 384 ALUs. The A6 series also supports Dual Graphics but according to AMD, they arenít recommending its use for Dual Graphics systems since the actual performance benefits will be minimal at best. This is likely due to the 192 ALUs utilized in its HD 8450G graphics processor. Naturally, the entry level A4 wonít receive Dual Graphics technology due to its focus on lower price points.
Sea Islandsí architecture and Richlandís design may not share much in common from an engineering standpoint but their respective specifications may hint at how AMD created harmony between two dissimilar product generations. Like the Mars Pro, XT and LP, the A10 comes with 384 cores and when combined with the higher clock speeds granted by the Richland refresh, allows the IGPís performance to roughly equal that of GCN-based discrete chips. Both are also seen as HD 8000-series by AMDís Catalyst drivers so there wonít be any conflicts there. Hence, it was just a matter of getting the two different architectures communicating with each other; a noteworthy accomplishment which deserves more credit than this small article can provide.
The exact details of how AMD accomplished this mixed architecture Dual Graphics wizardry are a closely guarded secret but supposedly the technology has been around for some time now. Richland simply represents the first time they were able to use it for meaningful performance enhancements.
How this will translate into the desktop space is anyoneís guess right now but we fully expect Richlandís upcoming APUs to also be compatible with GCN discrete cards like the HD 7000-series and OEM only HD 8000-series.
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