02-13-2009, 04:02 AM
The numbers you're getting are about right. AT&T advertises the maximum sync speed, not accounting for overhead. As mentioned, ATM overhead of ADSL is greater than cable.
Also, Comcast generally adds extra to the speed they advertise to account for overhead. For example, Comcast's 6Mbps tier is actually provisioned at 6600Kbps. As much as I hate Comcast, I have to give them credit for getting that right. (But they lose points bigtime because their PowerBoost gimmick isn't a sustained speed.)
On the other hand, AT&T U-Verse DSL is different and doesn't have as much overhead so speeds with U-Verse are pretty close to the advertised rate.
Also, Comcast generally adds extra to the speed they advertise to account for overhead. For example, Comcast's 6Mbps tier is actually provisioned at 6600Kbps. As much as I hate Comcast, I have to give them credit for getting that right. (But they lose points bigtime because their PowerBoost gimmick isn't a sustained speed.)
On the other hand, AT&T U-Verse DSL is different and doesn't have as much overhead so speeds with U-Verse are pretty close to the advertised rate.