XO 1.5 - CONTENTION WINDOW
fmiceli at plan.ceibal.edu.uy
Wed Dec 2 07:06:58 EST 2009
I'm looking directly at the registers in the XO 1.5 B2 laptop.
The process I follow is the following one:
# mount -t debugfs null /mnt
# cd /mnt/lbs_wireless/eth0/
To read register 0x0000
# echo 0x0000 > rdmac ; cat rdmac
MAC[0x0] = 0x0033fa05
I've read the following registers:
0xA0A0 - CWMin queue 0
0xA0A4 - CWMax queue 0
0xA0A8 - CWMin queue 1
0xA0AC - CWMax queue 1
0xA0B0 - CWMin queue 2
0xA0B4 - CWMax queue 2
0xA0B8 - CWMin queue 3
0xA0BC - CWMax queue 3
Now, this are the four queues I've read, and they have the values:
CWmax = 31
CWmin = 7
The eight registers that follow this ones have the exact same pattern (7 31
That's why I mentioned eight queues (but I might be wrong and those other
"queues" could be backups of the first ones).
2009/12/2 Daniel Drake <dsd at laptop.org>
> On Wed, 2009-12-02 at 09:33 -0200, Franco Miceli wrote:
> > What I was expecting was to have CWmax closer to 1024.
> > What I think happens when you set CWmax to 31 is that -as you have
> > more and more machines trying to compete for the medium- you could be
> > having more colisions -since they would wait less time slots to tx and
> > collisions would be more likely to happen.
> > When you set CWmax to a higher value you prevent this situation. Of
> > course this is for a higher number of machines using the medium.
> Could you directly reference the code that you are referring to, and the
> register documentation that you are looking at?
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