8 MHz Tx Bandwidth... What am I still missing?

Hi,

what I’ve done so far is:

–buy a new hardisk (a 7200 rpm sata), used only for the data to be
transmitted, and XFS formatted
—check my PC’s USB bus via gnuradio benchmark_usb.py, which says
everything is ok up to 32MB/s (output follows)
—use short int interleaved I/Q instead of gr_complex

but still a 342958080 bytes long file, meant to last 10.717 seconds if
played back at 32 MB/s (8 complex Msps)
lasts 13+ seconds while, instead it should be:

342958080 / 32e6 = 10.717 seconds

samples are damn slow to come out…this is quite frustrating as my
application needs a true 8 MHz bandwidth…

scaling down to 4 MHz is instead fine… as I really get the right
342958080
/ 16e6 = 21.435 seconds

what else should I check/modify? any hint?

the file meant to last 10.717 secs if played back with usrp_interp = 16
is
at
http://wwvince.interfree.it/of.dump

please, if anybody manages to send it out in not more than 11 seconds,
le me
know…
it would be really good news…

thanks

vincenzo

BENCHMARK_USB OUTPUT:

[[email protected] gr-mystuff]# ./monitor.sh
Testing 2MB/sec… usb_throughput = 2M
ntotal = 1000000
nright = 986311
runlength = 947654
delta = 52346
OK
Testing 4MB/sec… usb_throughput = 4M
ntotal = 2000000
nright = 1997961
runlength = 1997961
delta = 2039
OK
Testing 8MB/sec… usb_throughput = 8M
ntotal = 4000000
nright = 3997979
runlength = 3997979
delta = 2021
OK
Testing 16MB/sec… usb_throughput = 16M
ntotal = 8000000
nright = 7997477
runlength = 7997477
delta = 2523
OK
Testing 32MB/sec… usb_throughput = 32M
ntotal = 16000000
nright = 15995879
runlength = 15991525
delta = 8475
OK
Max USB/USRP throughput = 32MB/sec

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