Frame buffer/nano-X speed issues.

As the standard NEEK FPGA design does not provide any hardware acceleration, this is bound to be slow. It would be nice to have an improved design that does have hardware acceleration (plus the necessary driver), but I don't think anybody tried to create one yet.

-Michael

So are you suggesting that the problem is understood and that it is not an issue with nano-X but more likely with the hardware/software associated with the frame buffer itself? Thanks Michael. -Alex

NIOS is not a really fast processor. Without hardware acceleration X-like stuff many things can't perform too well, as the processor needs to create any single pixel on the screen, including hiding and redisplaying stuff that is hidden behind other objects, filling complex polygons for TTF types etc.

Any PC uses hardware acceleration for any type of X display, as even the PC processor is slow with low level pixel operations.

-Michael

You can modify the kernel driver altfb to use cached display memory instead of the uncached ioremap. It will be a lot faster.

- Hippo

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Hi, until now we have been ignoring the fact that the video update rate using the frame buffer wiki and a neek is slow. Has anyone looked into this enough to figure out where the bottleneck is? Has someone found a solution? Or am I doing something wrong? THanks in advance -Alex

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Hi Alex,

you should do some quick math to check whether your RAM memory interface is the bottleneck. Remember that the framebuffer area is in the same physical memory as your data and instructions (of course caches could change things somewhat).

In one system I've seen, the VGA controller was using the memory 90% of the time, and all other peripherals had to dispute with each other to get a share.

If your RAM is 16 bits wide, things could be even worse, because it would take two memory accesses to fetch a 32-bit word.

Cheers,

Ricardo.

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You can modify the kernel driver altfb to use cached display memory instead of the uncached ioremap. It will be a lot faster.

- Hippo

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Hi Hippo,

would like to know what modification have to be done exactly, to use a cached display memory?

Thx

D.