Hello Michael,
our FPGA hardware and kernel image were developed around the wiki example
for the DE2 board (unfortunately, we don't have any NEEK around yet).
We got good response times using nano-X only (this is, without FLTK).
Windows displaying only text strings were updated almost immediately. As for
dragging a window around on the screen, it was also performed very fast. We
noticed that increasing Nios cache memories had a great effect on this.
I wish I knew more about this whole "blit" thing, since it always comes up
when people are discussing performance issues. From what I've read in the
Nano-X Architecture document, it consists in drawing things off-screen and
later performing a fast copy to the framebuffer memory. This raises a few
questions:
1) How exactly does it make things run faster? Aren't we just adding
another step to the process? As I understand, in our hardware the system's
video memory is just a region in the SDRAM chip. The uClinux/nano-X screen
driver simply writes to it. Then the video controller hardware reads this
same region via DMA and generates SVGA signals. If we had two different
memory chips working at different speeds, I would agrre that this could make
things faster, but in our case it this necessarily true?
2) I agree that with the FPGA we have a great flexibility and it would
be relatively easy to change the hardware if we have to. Can you give an
idea of what this hardware accelerator should do?
Thanks for your comments and ideas,
Ricardo.
2009/3/13 Michael Schnell <mschn...@lumino.de>
> I'm not an expert on this at all, but I do have a nano-X application
> running on NIOS (in fact a NEEK dev-kit). If you have a NEEK, to you might
> want to try it, it's available in the Wiki as an Altera Application Loader
> application.
>
> Here I move a text window around on the screen. It uses about a quarter of
> the screen and after the location change it in fact needs two seconds for
> updating the screen.
>
> I suppose the only way to speed this up is providing hardware support
> instead of doing a "dumb" framebuffer. AFAIK, nano-X does support hardware
> accelerated screens and it should be quite easy to to hardware support for
> things like "blit" in the FPGA.
>
> -Michael
>
--
-------------------------------------------------------
Ricardo Pereira Jasinski
jasin...@utfpr.edu.br
Tel: (41) 9955-2852
LME - Laboratório de Microeletrônica da UTFPR
UTFPR Microelectronics Lab
www.lme.cpdtt.cefetpr.br
Tel: +55 41 3310 4756
