QNX RTOS v4 Knowledge Base
QNX RTOS v4 Knowledge Base
| Title |
Slowness with advanced video driver routines |
| Ref. No. |
QNX.000005990 |
| Category(ies) |
Video, Development |
| Issue |
We have found that when drawing a bitmap of about 500 by 400 pixels, the refresh speed is quite slow. You can actually see the screen being redrawn down the screen. We have tried using both the SVGA and Chips drivers. Neither of these drivers seemed to make a difference.
Are there any routines that directly access the video memory to improve the speed?
Does the video driver use video paging?
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| Solution |
Performance improvement would depend on the type of operation being done. The Pg.chips driver will be able to fill rectangles faster, but as far as drawing images is concerned, the two would be almost the same.
Using the 0xA0000 aperture is _not_ good.
If the chipset does not have enough
address lines (like in the old days), then you need to map in a 64K chunk of video RAM into the 0xA0000 aperture, and switch to a different memory bank when you need to access another area of the screen.
The chip is mapped (by the video BIOS) to 0x03000000, which is good. It means we never have to switch banks to access different areas of memory.
If there are no Hydra.ms entries, then you are using an older Photon. You may want to upgrade just the video drivers. Pg.flat is much faster than Pg.svga and the same improvements are in the newer Chips drivers.
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