Příspěvek
od delarock » pát 04. čer 2010 17:55:37
Konkretne :
But let’s move on to what’s really important; the graphics processing power of the Hummingbird in the Samsung Galaxy S versus the Snapdragon in the EVO 4G. It’s quickly apparent that Samsung is claiming performance approximately 4x greater than the 22 Mt/s the Snapdragon QSD8650’s can manage. It’s been rumored that the Hummingbird contains a PowerVR SGX 540, but at 200 MHz the SGX 540 puts out 28 Mt/s, approximately 1/3 of the 90 Mt/s that Samsung is claiming. Either Samsung has decided to clock an SGX 540 at 600 MHz, which seems rather high given reports that the chip is capable of speeds of “400 MHz+” or they’ve chosen to include a multi-core PowerVR SGX XT solution. Essentially this would allow 3 PowerVR cores (or 2 up-clocked ones) to hit the 90 Mt/s mark without having to push the GPU past 400 MHz.
Unfortunately however, this brings us right back to the memory bandwidth limitation argument again, because while the Hummingbird likely uses LPDDR2 memory, it still only appears to have single-channel memory controller support (capping memory bandwidth off at 4.2 GB/s), and the question is raised as to how the PowerVR GPU obtains the large amount of memory bandwidth it needs to draw and texture polygons at those high speeds. If the PowerVR SGX 540 (which, like the SGX 535 performs at 28 Mt/s at 200 MHz) requires 4.2 GB/s of memory bandwidth, drawing 90 Mt/s would require over 12.6 GB/s of memory bandwidth, 3 times what is available. Samsung may be citing purely theoretical numbers or using another solution such as possibly increasing GPU cache sizes. This would allow for higher peak speeds, but it’s questionable if it could achieve sustainable 90 Mt/s performance.
Android: M.Milestone - Nexus One - Galaxy S - Desire HD - Galaxy s II - Galaxy Nexus Palm Pre, Xperia X1, motorola V3, motorola V8, Iphone 2g, iphone 3G, iphone 4,