Raspberry Pi review
April 16, 2012 | 14:24
Companies: #arm #broadcom #hynix #raspberry-pi #raspberry-pi-foundation
While the 700MHz CPU in the Pi's BCM2835 chip might be a trifle underwhelming, its graphics performance is anything but. Using the Broadcom VideoCore IV GPU, the Pi has some serious horsepower under its hood with full support for OpenGL ES 2.0 acceleration, hardware decoding of h.264 video and plenty more besides.
It's the reason the BCM2835 exists, in fact: the chip was originally developed for use in multimedia-heavy environments such as portable media players and set-top boxes. Based purely on multimedia performance, the BCM2835 is claimed to be around four times as powerful as the processor in the iPhone 4.
Having the multimedia performance on-hand is one thing, but actually using it is quite different. Currently, the majority of operating systems designed for the Pi are in the very early stages of development - hardly surprising, given that the device has only just begun to ship in any meaningful quantity.
Without hardware-accelerated drivers, graphics performance is poor.
The result is a wealth of power which the system just isn't programmed to use. Hardware accelerated 3D is possible, but tricky - and absent from the default Debian distribution altogether. Distributions like XBMC have had more luck accessing the h.264 decoder, and full-screen 1080p30 playback has been proven possible, but it's again not something which is standard to the default distribution.
Worse still, to get the maximum performance for 3D acceleration out of the BCM2835 you need to give it a larger chunk of the shared 256MB RAM. For full 3D acceleration at 1920 x 1080, the Foundation recommends a 50:50 split - leaving you with just 128MB for the host operating system.
That's not to say that it's not doable: Quake III has been proved to run on the Pi in high definition at a more than playable framerate. Until general-purpose distributions ship with 3D acceleration and hardware media decoding enabled by default, however, it's something which will remain the preserve of hackers and tinkerers.
It's the reason the BCM2835 exists, in fact: the chip was originally developed for use in multimedia-heavy environments such as portable media players and set-top boxes. Based purely on multimedia performance, the BCM2835 is claimed to be around four times as powerful as the processor in the iPhone 4.
Having the multimedia performance on-hand is one thing, but actually using it is quite different. Currently, the majority of operating systems designed for the Pi are in the very early stages of development - hardly surprising, given that the device has only just begun to ship in any meaningful quantity.
Without hardware-accelerated drivers, graphics performance is poor.
The result is a wealth of power which the system just isn't programmed to use. Hardware accelerated 3D is possible, but tricky - and absent from the default Debian distribution altogether. Distributions like XBMC have had more luck accessing the h.264 decoder, and full-screen 1080p30 playback has been proven possible, but it's again not something which is standard to the default distribution.
Worse still, to get the maximum performance for 3D acceleration out of the BCM2835 you need to give it a larger chunk of the shared 256MB RAM. For full 3D acceleration at 1920 x 1080, the Foundation recommends a 50:50 split - leaving you with just 128MB for the host operating system.
That's not to say that it's not doable: Quake III has been proved to run on the Pi in high definition at a more than playable framerate. Until general-purpose distributions ship with 3D acceleration and hardware media decoding enabled by default, however, it's something which will remain the preserve of hackers and tinkerers.
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