On Jun 23, 2006, at 2:03 PM, Mathieu Bouchard wrote:
On Fri, 23 Jun 2006, Hans-Christoph Steiner wrote:
As for the usage of CPU, because its a fast bitrate, it will
always use a noticeable amount of CPU time. Mouse data is another
example of a high-speed data stream.old mice ran at 1200 bps. PS/2 mice might run at 9600 bps, not
sure. In any case it doesn't get over 1 kilobyte/sec. Each packet
is 3 or 5 bytes depending on the protocol. I find it likely that
most PS/2 mice use only a small fraction of the bandwidth, but I
haven't measured.
IIRC, a lot of mouse pointer processing is handled by the
graphics card for this reason."Just" the display of a sprite such as an arrow. If you ever use a
plain VGA driver, you don't have this feature, so it has to be
handled software.What makes you think it's high speed? Or do you mean an example of
something that needs to have a low latency?
PS/2 mice can run up to 200Hz, USB HID devices up to 100Hz. With USB
HID mice, the data is sent every 10ms, but its not just one report,
it can be many. Each USB HID device is allocated 64kbps of
bandwidth, and decent mice use it.
My Logitech MX510 sends 1 byte for buttons, 2 bytes for standard XY
reports, and 3 bytes for hi-res XY reports (12bits per axis). That's
6 bytes per report. It can send up to 64 reports per poll (every 10
ms), so it has the ability to overwhelm the USB HID allocation many
times over. This is something that I have measured.
.hc
Using ReBirth is like trying to play an 808 with a long stick. - David Zicarelli