On 23-Mar-2000 Richard Stover wrote:
>
> On my own project, we need to run at something close to
> the rated 2 megabyte/sec capacity of ECP mode. But the
> dma hardware seems to run at 2 microseconds/byte on the
> system I'm using (4 times slower than our goal). Since this is
> the first PC I've looked at in this detail I don't know if this is
> going to be typical. Do you have any experience in this
> area? Are there faster dma controller chips? Or is this set
> by some old standards (like ISA)?
I wrote a dma-handler for webcams based on the CPiA chip by VLSI. The
maximum thruput I get right now is about 500kilobytes/sec with a 2.2.x
kernel. I was told by the windows-driver writers, i.e. by the company that
made the chips, that they got at least 800kilobytes/sec which is still way
below the 2MB you refer to. I did not really try to tune the stuff. So I
have no idea if the bottleneck is driver-software, hardware or the
linux-kernel. Also I can use only 8bit DMA (i.e. I cannot assign a DMA>4
to the parport). A 16bit DMA might boost performance for you. But I guess
you need special parport-hardware for that. I have just a an standard
Asus motherboards with onboard parport-controllers.
-Peter
-------------------------------
Email: Peter.Pregler@risc.uni-linz.ac.at
WWW: http://www.risc.uni-linz.ac.at/people/ppregler
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