[PATCH][RFC] usbatm.[ch]: cleanup and OAM F5 loopback

matthieu castet castet.matthieu at free.fr
Sat Mar 12 17:10:03 EST 2005

Hi Roman,

Roman Kagan wrote:
> Nonetheless please let me reiterate the question I asked a while ago: do
> you have an indication that isochronous transfers are better for this
> sort of workload?  I'd be surprised if they are.  They are meant for
> constant rate data streams with no requirement for data integrity, like
> audio or video.  ATM data, on the opposite, is typically variable rate,
> and loosing data on the way from the modem to the host doesn't look
> nice.
Well, may be it is the sagem that don't work well with bulk mode, but 
when it is in high speed mode, if you reach a limit (200-300kb/s), the 
modem produce lot's of error, and the atm data trame are broken (crc 
error, bogus pdu_length, ...). So because of these errors, the modem 
never reach the maximun rate.

In iso rate it work at 700kb/s with no problem.

> Please note that I'm just handwaving here; AFAIK SpeedTouch 330 has iso
> endpoints too, but I'd be really interested to see if it helps a single
> bit...  Maybe eagle-usb project has done some measurements?
Like I said 300-400kb/s vs 700kb/s on my computer.
I don't know if there are other measurements.


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