It only updates every few seconds because the device requests an update.
To illustrate, we know the SNR by its very nature varies continuously, as it is an analogue item. It is fair to assume the SNRM itself updates in line with that, but it is not guaranteed that it does. It may be a digital calculated figure from the SNR.
It is clear that as SNR varies the max attainable varies as an analogue value, but the more one thinks about it the less feasible it becomes for the modem to know what it is. It would have to be running a calculation loop. It isn't an intrinsic part of the connection protocol.
When looking at stats on a device the figures change at fixed intervals, not continuously. The update occurs because the device requests a refresh from the modem. Exactly like all the monitoring programs. Even the GUI on a combo device does not continuously update.
There is no reason to assume the max attainable is calculated at sync-time, nor that it is continuously recalculated. It is not a figure of any use to the functioning of the modem. There is every reason to believe it is a display figure calculated on demand.
To say "it's continually calculated whilst the line is in sync as line conditions change" and "it's blatantly obvious that it updates when the line is active" has to be nonsense. It would make calculating it more important than maintaining sync, bit-swapping, and passing data.
The poster is asserting false detail, not chasing it.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - AAISP Home::1 80/20. Sync 63790/13596Kbps @ 600m. BQMs - IPv4
Edited by RobertoS (Fri 07-Apr-17 12:21:06)