I swapped out the modem for another unit. I plugged in a DLink DSL-320B-Z1 in fact, and straight away downstream sync rate is right up to ~2.8 Mbps at 6dB SNRM, so allowing for the fact that this is 6dB SNRM not 3dB like the other modems that is very much full speed.
So either that B10A has gone bad or it is just some weird thing to do with turning everything off and on again ? Suggestions ?
We had some lightning in the distance last month and some days later, on 1 Nov, line #4 or its modem started misbehaving, with reduced downstream sync speeds.
I picked a DLink simply out of convenience, because I have several at hand already set up, and although I have several ZyXEL B10As in my spares cupboard, I am not sure whether or not they have been configured etc yet, and I did not take the time to assess them. That is a job for when I am feeling a bit better.
Later on, I will retest the ZyXEL to see if it has really ‘gone slow’ ie permanently bad.
Do modems ever develop a disease of permanent slowness? Speculating, is it possible that part of the filter or analog front end can get cooked affecting the performance adversely, but the modem still functions, albeit in a substandard fashion? Or is it all or nothing with modems ?