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Posts: 2,102 | Thanked: 1,309 times | Joined on Sep 2006
#11
The reason is that it only comes with 5Mbits of VRAM which is nowhere near enough for the 800x480x16 resolution. So Nokia had to use an external LCD controller (Epson Blizzard or Hailstorm I think), which is the reason for the not so great video performance (bandwidth to/from the CPU is slow).
But is that 5Mbits just an on-chip framebuffer? I see no mention of whether the PowerVR has its own dedicated memory, shares that framebuffer memory (which is unlikely as it would be hard to fit full screen display + intermediate structures into that space) or accesses the main memory (which I think is most likely).

If the powervr memory is in fact part of the standard RAM, there's no reason why its output can't be copied into the LCD controller framebuffer. This will still have the same bandwidth issues, but the point of the 3D hardware isn't to do more frames, it's to cut the cost of doing the 3D transforms on the data.
 

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#12
http://focus.ti.com/pdfs/wtbu/TI_omap2420.pdf says the 5Mbits supports a VGA framebuffer for example
 
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#13
http://www.imgtec.com/PowerVR/Produc...hics/index.asp

Specifically:

"PowerVR cores use an on-chip tile buffer to keep all bandwidth-intensive pixel processing on-chip, where it can be executed most cost effectively and efficiently.

Memory bandwidth requirements are minimized by eliminating all Z-buffer traffic between the 3D core and external memory, and by ensuring that only visible pixels are ever written to the frame buffer. "

So, no reason to expect it not to work on something like the N800/N810 with an external framebuffer.

Though it does ask the question of whether or not the last sentence is to be interpreted literally, in which case the data would need to be copied from the 5Mbit omap on-chip framebuffer to the lcd controller framebuffer.
 

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#14
Originally Posted by lma View Post
why else would they spend time making hildon resolution-independent earlier this year?
video-out at higher res
 
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#15
Originally Posted by ArnimS View Post
video-out at higher res
Hildon's being used for UMPC-Linux, which runs on those 1024x600 screens, mostly.
 
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#16
I thought the N800 had DMA (Dynamic Memory Architecture) just like all the other Symbian phones. Why would they only give 5mbits of VRAM to it when it can use whatever memory is available?
 
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#17
Oh!! You guys mean the 5mbit SRAM?? That's not VRAM that's an on-chip tile?buffer which is extremely fast (maybe faster than Embedded RAM).

Last edited by M03Z; 2007-11-16 at 10:11.
 
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#18
Originally Posted by M03Z View Post
I thought the N800 had DMA (Dynamic Memory Architecture) just like all the other Symbian phones.
The N800 is _not_ a Symbian phone!
__________________
N800/OS2007|N900/Maemo5
-- Metalayer-crawler delenda est.
-- Current state: Fed up with everything MeeGo.
 
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#19
Originally Posted by TA-t3 View Post
The N800 is _not_ a Symbian phone!
Yes, but it uses the same chip that is used in 3 top Symbian phones i.e. n93/n95/n82 so in other words, hardware-wise it is.
 
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#20
Well I've got the pvr.ko driver to load and it looks like it has initialised at least (working entries under the sysfs). The other libraries and binaries that came with it are all compiled for the old abi though unfortunately.
 

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