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Tech Focus: IMG on PowerVR mobile graphics

IMG talk graphics tech featured in iPad 2 and Sony NGP

Digital FoundryWhat anti-aliasing modes are supported in PowerVR architecture and what are the associated performance costs? Can we expect high IQ (4x MSAA) on PowerVR SGX543 MP4 as being commonplace at a 960x540 resolution?
IMG

As mentioned before anti-aliasing (AA) was one of the key focus areas for Series5XT and the impact on performance is as low as possible without sacrificing image quality. We fully expect that AA will be enabled for the majority of content going forward due its low impact as can be seen on glbenchmark.com where the difference between AA on/off is just small performance fluctuations due to background tasks.

Digital FoundryStereoscopic 3D is swiftly being embraced by many different types of media, with games taking the spearhead. Does PowerVR architecture offer any specific advantages that makes 3D easier to work with?

Anti-aliasing was one of the key focus areas for Series5XT and the impact on performance is as low as possible without sacrificing image quality.

IMG

The additional workload required for S3D places significant additional demands on the graphics processor - and PowerVR SGX is more than up to the task. PowerVR SGX graphics acceleration cores are ideally suited to S3D graphics, either using single or multi-processor cores for resolutions up to full 1080p HD, and are capable of supporting all commonly used S3D formats such as frame sequential, side-by-side, top-bottom and interlaced.

Using SGX it is possible to quickly upgrade existing 3D content to deliver full S3D, bringing new realism to 3D games and navigation, and exciting new possibilities for user interfaces in a wide range of applications. The PowerVR SGX tile-based deferred rendering architecture is ideally suited to deal with the increased demands of S3D - which include twice the geometry processing workload and commensurate increases in fill/texturing workload. The scalable nature of the SGX architecture and its ability to efficiently support multiple contexts ensure that the best possible S3D user experience can be achieved using SGX powered devices while maintaining SGX's unique low power, high performance credentials.

Digital FoundryBearing in mind the importance of battery life, what kind of correlation is there between the clock speed of your GPUs and the fabrication process? Any real life examples you can talk about where die-shrinking the tech has allowed for faster clock speeds with the same power draw?
IMG

As Imagination delivers soft IP it can be targeted at any process technologies and this is very much an area where our customers have a lot of knowledge and unique benefits allowing them to differentiate their solutions even when based on the same GPU core.

Just as a reference, over time we have seen implementations of the same SGX core going initially from 110MHz to 200MHz and today designs are beyond 400MHz in silicon. Clock frequencies versus higher-end cores is a key choice for our partners and this is often impacted by their silicon process capabilities and benefits and as a result we have seen some customers doubling performance via clock frequency and others have doubled performance by going to a higher end core.

Digital FoundryImagination Technologies have experimented with some novel texture formats before. What has happened to this line of technology, and where is it headed?
IMG

Imagination has always recognised the need for high quality but low memory footprint and bandwidth textures and images and in the old days we offered Vector Quantization approach for Dreamcast which offered on average 5:1 compression ratio.

With PowerVR MBX and SGX we offer PVRTC texture compression down to 4 bits per pixel (8:1) and 2 bits per pixel (16:1) compression for both RGB and RGBA formats. These PVRTC formats are very popular with developers since they offer a much better compression ratio than using PC formats such as DXTC which requires 8 bits per pixel for RGBA formats meaning POWERVR based products can have up to 4 times lower memory footprint and bandwidth usage (= power usage) compared to competing products. Without a doubt this is an area where Imagination will continue to make investments and announcements will be made in due course.

Digital FoundryOut of interest, Sony says that it has a PowerVR SGX543 MP4+ inside Sony NGP... what does the plus stand for?
IMG

That's to indicate the work Sony has done to implement the graphics. What they licensed is a SGX543 MP4.

Digital FoundryYou have other multi-core projects in the pipeline for the series five hardware. What advantages do they have over the SGX543?
IMG

In addition to SGX543 we have also announced SGX544 which offers the same performance characteristics but enables fully compliant DX9 Feature Level 9_3 capabilities so basically an extra bump in feature set to meet Microsoft requirements. Also available is the SGX554 which is our first 8 pipeline part (SGX543/544 have 4 processing pipelines) which offers improved compute density for customers focused on GP-GPU and shader processing since a single SGX554 would offer the same compute capability as an SGX543 MP2 but not the same geometry or pixel throughput.

This means that SGX554 offers more GFLOPS per mm2 since the design avoid overscaling the geometry and pixel capabilities of the design versus customer requirements - basically we do not believe in "one size fits all" solutions and we thus offer our customers various options.

Digital FoundryThe future of the SGX tech is in your series six "Rogue" platform. What are your overall objectives for this architecture and what kinds of products are you targeting it for?
IMG

Imagination's next generation PowerVR Series6 architecture, codenamed "Rogue", has now being licensed by multiple lead partners. Rogue delivers unrivalled GFLOPS per mm2 and per mW for all APIs. We see it crossing a very wide range of markets.

ST-Ericsson has announced that its new Nova application processors will include Imagination's next-generation PowerVR Series6 Rogue architecture but we've not really announced much detail of Rogue yet - I'm afraid it's "wait and see".

Digital FoundryFinally, we see Apple talking about a 9x performance increase from iPad 1 to iPad 2 and benchmarking of the devices sees at least a 4x "real world" boost in GPU performance. With SGX535 as the baseline, what are your performance targets for your hardware going forward. I'm sure I read somewhere you were looking at a 100x increase within five years...
IMG

Yes we are.

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Richard Leadbetter avatar
Richard Leadbetter: Rich has been a games journalist since the days of 16-bit and specialises in technical analysis. He's commonly known around Eurogamer as the Blacksmith of the Future.
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