On Tue, Feb 24, 2009 at 01:07:34PM -0500, Marcus D. Leech wrote:
Eric Blossom wrote:
Marcus, in my experience, USB performance has not be limited by cpu
cycles. It seems to be primarily a function of the design of the host
controller, the firmware in the device, and a reasonable way to get
the data into user mode. In most apps I've benchmarked, the overhead
of all usrp related stuff is typically on the order of 5 to 10% of the
total cycles consumed.
Eric
OK, so improving total USB cycle counts in user mode from 10% to 5%
perhaps wouldn't noticeably improve
things like overruns--is that what you're saying?
Overruns are generally caused because your signal processing can't
keep up, not that there's a problem with handling the USB.
So, in your experience what is the sh*t-hottest USB controller out
there, and is it available on a PCI or PCI-E card?
Once the controller can handle 32MB/s, you're golden. Pretty much any
of the onboard controllers over the last few years work fine.
Measure twice, cut once. Time be time.