Cisco 877 SNR Adjustment

Go into global configuration mode and type the following:
service internal
int atm 0
dsl noise-margin (a value between -3 and 3)
The service internal command exposes the dsl noise-margin command (and other hidden/non standard commands). The dsl noise-margin forces the router to training at a higher noise margin (sacrificing speed for stability). Setting this to 3 for example should see you get a higher noise margin, slower speed (and depending on firmware) a higher attenuation.
Start at 3 and work your way down to 0 in 0.5 steps until you get a stable connection. A value of 0 is the same as not having this command at all (eg: normal settings).
If you add a dsl noise-margin command, after a reload you’ll see “WARNING: Unsupported Command. May cause violation to ADSL standards.” on bootup, ignore it, it’s just the addition of the noise-margin command.
Use the dsl noise-margin command to fine tune your connection to get that extra stability if required.

The default value of  noise-margin is 0, I find -3 igive me the best download speed (3776 kbps) compares to default settings (3220 kbps).

The Alcatel firmware fireware also related to the sync speed: FW4.0.15 in IOS 15 only sync to 3000 kbps whereas FW 3.0.14 in IOS 12.4 can sync to 3200 kbps

Ref: http://www.alcatron.net/?cat=7&paged=2