ADSL Upload Sync

Hi,
Curious about a variance in the upload syncs from a few different adsl lines I monitor
the download syncs are pretty good and so are the uploads
Line 1 Max Observed Downstream Speed (Mbps) 11.86
Max Upstream Observed Speed (Mbps) 0.89
Line 2 Max Observed Downstream Speed (Mbps) 12.59
Max Upstream Observed Speed (Mbps) 0.89
Line 3 Max Observed Downstream Speed (Mbps) -- 20.94
Max Upstream Observed Speed (Mbps) -- 0.89
Line 4 Max Observed Downstream Speed (Mbps) -- 12.6
Max Upstream Observed Speed (Mbps) -- 1.17

Why the upload of 1.17 on line 4, and not lines 1-3? 4 is about 3km from exchange and the longest line in my reckoning, yet it has the best upload? whereas lines 1-3 are within 2km from exchanges and have the standard .89Mbps sync
other than that no issues with these lines pretty stable and all above 10Mbps
lines 1,2,4 are on one exchange and 3 is on another

The most likely cause would be different profiles on the CP equipment in the exchange.

If the upload link is interleaved then the sync speed is 888kbps. Line 4 must be on fast path giving a higher sync speed.

Plus variations in ADSL2+ modem

In reply to a post by Realalemadrid:

If the upload link is interleaved then the sync speed is 888kbps. Line 4 must be on fast path giving a higher sync speed.

I think that depends on the ISP involved. The only one I know of personally with that setting is Plusnet, and they will, or used to, remove that cap on request.

No others.

I have as of yesterday setup lines 1 and 2 to be on a UPS
and two weeks ago before this i changed the sockets and filters, so now in theory over time the lines should be seen as stable by the DLM even when a quick power outage, as the routers stay up now instead of dropping so in theory the only disconnects there should be are exchange based or line faults, both lines clear on quiet test, so only time will tell as to if the dlm acts and speeds the lines up any more
they have been increasing in download sync for a few months now, used to be 8-9Mbps on line 1 and 2, now up in the 11-12
fingers crossed and thanks for replies,
all connections are via BT btw. not LLU