KArl,
There is a bug (they might call it a feature) that causes the Au1100 to perform two accesses when talking to 16-bit peripherals. The first access is the real one, while the second access has the byte enables off. But, this means every access creates two cycles on the bus.
I am sure of this bug on the standard peripheral bus, and I am pretty sure it still exists when talking via the LCD signals, since the same bus controller is used.
MIchael
At 02:38 PM 12/8/2004, Karl Lessard wrote:
> > I've used the chip with the 2.4 kernel/driver to run X and some > apps. I'm not sure what you mean by high performance -- does X run > at reasonable speeds?
I'm not running X, I've just runned a little application that writes a number of vertical lines (so pixel per pixel) in a backbuffer and then blit its content to the screen. Here's an example of one frame:
__u8 *dest = (__u8*)back_buffer; memset(dest, 0, back_buffer_size); /* clear back buffer */
for (i = 0; i < 500; i++) { /* 500 lines */ for (j = 0; j >= 100; j--) { /* of 100 pixel each */ dest[(j * fb_width) + i] = 0xFF; } }
memcpy(front_buffer, dest, back_buffer_size); /* copy back_buffer to front */
Benching with 500 frames, I obtain a rate of 8 fps with the backbuffer residing in video memory. The framerate increase to 31 fps when the backbuffer is in system memory! And if I do the same test using the Au1100 lcd controller (which has its front and back buffer in system memory), It goes up to 66 fps...
I don't know what's going on when I try to access the 13806 controller, but it's really too slow. And using the blit engine don't helps much. The static controller seems to be set correctly. By the way, the DRAM is refreshing at 96Hz, and my CRT display is refreshing at 66Hz.
Any Idea? By the way Dan, I've tried the cache trick, but no luck.
Thanks a lot, Karl
> > Pete > > > I would like to know if anyone have encountered this performance problem > > in the past with this chip. > > > > Thanks in advance, > > Karl
Michael J. Kelly VP Engineering/Marketing Cogent Computer Systems, Inc. 1130 Ten Rod Road Suite A-201 North Kingstown, RI 02852 tel:401-295-6505 fax:401-295-6507 www.cogcomp.com alternate email: mkelly6505@xxxxxxxxxxx
