What we didn't know we found out why.
person posted in the direct forum kind of disappointed his pro speeds were not higher, and he was losing sync. It seems the computer's power supply was the culprit. This person was still at 2496/512 speeds but as you can see the capacity went down 10% and the noise margin went up 4db.
Morale of the story: Be sure to check for interferences you can, and cannot see. In this test an A.M. radio might have been able to detect this. A good power conditioner would probably be a good idea here as well.
Before
-----------> 2008-12-26 14:17:05 <------------
DSLAM PROFILE ADV_2496_512_ILEAVE_M
LINE STATUS IS-NR
DOWNSTREAM <-> UPSTREAM
CAPACITY CAP 82 <-> 64
NOISE MARGIN NOI 10.0 <-> 16.0
TRANSMISSION PWR PWR 17.0 <-> 12.0
SIGNAL ATTENUATION ATT 51.0 <-> 34.0
MAX ATAINABLE RATE MAX 3072 <-> 832
CURRENT BIT RATE RTE 2496 <-> 512
CURRENT CELL COUNT 77641491 <-> 63941081
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explanation
I think I located the major source of SNR degradation. It seems that a PC power supply was generating noise and it was coupling through the house power to the phone lines. When it finally died and was replaced, the noise margin jumped to 15dB+/-1dB over a period of a couple of days. The 2wire modem's bit loading plot is almost ideal now. I think I'm ready for that final 3072kbps download speed increase.
After
-----------> 2009-01-05 16:18:49 <------------
DSLAM PROFILE ADV_2496_512_ILEAVE_M
LINE STATUS IS-NR
DOWNSTREAM <-> UPSTREAM
CAPACITY CAP 71 <-> 65
NOISE MARGIN NOI 14.0 <-> 15.0
TRANSMISSION PWR PWR 17.0 <-> 12.0
SIGNAL ATTENUATION ATT 51.0 <-> 34.0
MAX ATAINABLE RATE MAX 3584 <-> 832
CURRENT BIT RATE RTE 2496 <-> 512
CURRENT CELL COUNT 39090775 <-> 60438809
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