Re: [Libusb-devel] True Async Transfers on MacOS X?

[Charles L. <cl...@gm...>]

On 1/30/06, Michael Dickens <mdi...@nd...> wrote:
> after all, isn't USB 2.0's theoretical limit 480 M-bits/s =3D=3D
> 60 MBps?

480 Mbps includes all of the overhead of packetizing the data, so it's
definitely less than 60 MBps throughput.

Also, IIRC the GNURadio board uses an EZ-USB FX2, so you are probably
limited to the FIFO rate (48 MBytes/sec). Even then, you may not be
able to get that with bulk transfers. (Are you using bulk or
isochronous?)

I'm not sure about the internal vs external slowdown, though (most of
the time, I'm at the other end of the spectrum: increasing timeouts to
accomodate for low-speed transfers). Too bad there isn't an easy
equivalent of lspci in OS X to see what the latency settings of the
USB chips are.

--
- Charles Lepple