GDC last week was stiff with VR headsets and other virtual - and augmented – reality equipment, some of which I have reported on already but there was one interesting item I have had to keep under wraps until today’s official launch date.
The PowerVR team at Imagination briefed me on ‘Furian’ which they are calling the first new PowerVR architecture since Rogue was launched in 2010 and there is enough there to make this a very interesting event indeed. Imagination is aiming this new generation explicitly at the 7nm process node with VR, ADAS and notepad PCs in mind.
Where the Rogue architecture was designed for a 28nm process shooting for 60FPS gaming on 2MPixel screens, Furian* is looking for 120FPS on a 4K screen; capable enough to drive a low latency VR setup in a mobile configuration. In support of this, Imagination tells me that they have basically doubled everything: twice the fillrate and twice the SIMD width per cluster, which doesn’t get us to the 8x performance boost implied by the new frame rate and resolution targets but they assure me that with the improved scalability and performance density, that sort of performance is now achievable by adding more clusters within the power limits.
There are a lot of changes just to get the improved graphics performance (more of which elsewhere) but purely from the vision processing point of view, there are some intriguing developments. One of the more interesting is that down in the guts of the cluster where all the compute gets done, Imagination has split out what was a unified cache into separate texture, instruction and data cache memories, allowing them to take advantage of data memory banking to implement a scatter-gather scheme similar to that found on vision-specific DSPs. The rogue architecture was already able to implement lane swizzling and shifting, so this new feature brings Furian into a much more direct feature comparison with those cores.
The base ALU has also changed. Where Rogue has all its instructions going through a single path containing multiple arithmetic units as well as logic and other functions, Furian splits these out into an arithmetic-only path with a separate parallel path for everything else. Imagination does not claim that this path is simultaneous issue, so we’re not looking at some sort of hybrid SIMD/VLIW architecture but given that this secondary path is used for multi-cycle instructions, some degree of parallelism may be available and the simplified structures will certainly lend themselves to higher clock rates and/or lower power operation.
Vision algorithms typically work on fixed point and integer operands so any GPU that plans to compete needs to take that into account. The PowerVR series 7XT GPUs were equipped with separate integer ALUs operating in Vecn mode depending on whether 32, 16 or 8-bit operands were chosen and the launch materials for Furian specify that there is a Vec2 mode for FP16 operands but there is nothing on integer resources. Privately, Imagination has assured me that Furian inherits “some aspects” of series 7XT integer handling but without giving details. That’s a loose end that will need to be tidied up before we can really say how this generation will perform as a vision processor.
Imagination has been going through some tough times recently. They are still holding on to their prized position as sole GPU supplier to iOS products but that is both a blessing and a curse as the rest of the market gradually slips away to competitors with greater freedom of action. Will the new Furian architecture help them regain their lost market share? With projected headset sales in the single digit millions, VR is not going to do it for them even if they manage to deploy a ray tracing version but vision functions in mobile and automotive will only get more important and Imagination have traditionally had loyal support from TI, Renesas and Socionext.
According to Imagination, multiple licenses have already been taken and the designs delivered to customers so we should be seeing product announcements within a year. As usual, there is no hint as to who these customers might be but given that this is a high end XT architecture that really doesn’t play in the mid-range handset market of their usual customers, we should expect something from one of those automotive players.
*Yes, the name is something to do with Vin Diesel but for the sake of decency, I shall draw a veil over the mental process that linked Riddick to this GPU
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