On 09/03/2010 04:52 PM, Marc Epard wrote: > Sorry to reply to myself, but we just got the new Ethernet NIC so both USRP2s > report WE_TX flow control. Nothing changed. > > And I have a correction for the types of ethernet cards. The onboard NIC is > the Broadcom. Ethernet 2 (and now 3) appear to be Realtek RTL8111/8168B. > > On Sep 3, 2010, at 3:10 PM, Marc Epard wrote: > > I'll comment that a 1.6GHz machine that's getting close to 4 years old isn't particularly "beefy" by todays standards. Certainly not beefy enough to sustain two 25Msps threads without "problems".
Just the interrupt load alone is rather frightening. The packets used by the USRP2 aren't terribly big, something like 300-500 bytes I think. So, 25e6 / 3e2 = 83Kpackets/second--depending on your NIC, each of those packets could be creating an interrupt! Then you have to actually process the darn things -- copy up to user space, "do stuff", and present the result of that "stuff" either back out to the network, or into your software (FFT display, whatever). To give some perspective. I run my radio astronomy Rx-only "stack" on a 6-core machine doing "stuff" that's of the same order of complexity as modern telecom-type signal processing. At 5 or 6MHz bandwidth, the machine is working *really* hard. That's a machine with an AMD Phenom II X6 1090t, running at 3.2GHz/core with 6GB of *fast* memory. [And I suspect a flaky power supply, but that's a topic for another day :-) ]. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
