Raspberry Pi GPU doubles iPhone 4S performance

Raspberry Pi - the $25 credit-card sized computer - features an advanced graphics core that outperforms the GPU in iPhone 4S by a factor of two to one "across a range of content", according to claims made by the manufacturer in a new Digital Foundry interview published today on GamesIndustry.biz.

Discussing the graphical potential of the Broadcom BCM2835 chipset at the heart of the device, executive director Eben Upton describes how it compares to the graphics capabilities of the most popular mobile devices.

"I was on the team that designed the graphics core, so I'm a little biased here, but I genuinely believe we have the best mobile GPU team in the world at Broadcom in Cambridge," Upton says, when asked to confirm rumours that Raspberry Pi comprehensively outperforms NVIDIA's Tegra 2.

"What's really striking is how badly Tegra 2 performs relative even to simple APs using licensed Imagination Technologies (TI and Apple) or ARM Mali (Samsung) graphics. To summarise, BCM2835 has a tile mode architecture - so it kills immediate-mode devices like Tegra on fill-rate - and we've chosen to configure it with a very large amount of shader performance, so it does very well on compute-intensive benchmarks, and should double iPhone 4S performance across a range of content."

Broadcom's approach with the BCM2385 chip is somewhat different in other respects though - while its graphics core is state-of-the-art, its main CPU is a single core 700MHz ARM11: somewhat off the pace compared to high-end mobile devices, but still extremely powerful for a $25 computer. The Raspberry Pi Foundation hopes that the potential and flexibility of the device will bring about a new wave of homebrew coders akin to the programming revolution in the 80s spearheaded by machines like the BBC Micro, Commodore 64 and ZX Spectrum.

As the Raspberry Pi is based on an existing mobile part currently being deployed in the Roku2 video streaming player, the device should find favour with media enthusiasts too. Already, the device has been demonstrated running popular open source front-end XBMC. The Broadcom chipset features hardware acceleration that allows for h.264 content at 1080p Blu-ray quality to decode at 30 frames per second - a wonderful 'extra' for a device mostly aimed at boosting interest in programming.

"All the media features are to some extent a bonus, but they've been a part of our thinking ever since I joined Broadcom five years ago (having spent a year trying to build a $25 PC out of openly-available parts like Atmel microcontrollers)," Eben Upton explains.

"I think there's a lot to be said for a device which is useful for something other than programming. The media features provide a 'hook' to draw people to the platform; once we have them hooked, we can trick them into becoming programmers!"

Raspberry Pi will be available in Model A and Model B versions priced at $25 and $35 respectively - the more expensive version features 256MB RAM up against the 128MB of the Model A with the added bonus of an in-built Ethernet port. The first batch of 10,000 units is currently in production and should be on sale shortly.