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DSL modem chipset issue comes to the fore
Tuesday 23 October 2007 10:20:51 by Andrew Ferguson

The Register is claiming an exclusive on the reliability of an ADSL modem chipset that is in use around the world. Our forum has had information on this topic pre-dating The Register article, and there is frequent discussion with regards the reliability of many different pieces of ADSL kit in our DSL Hardware forum.

It needs to be said that one of the problems with ADSL around the world is its use of the AM radio band frequency range, which makes it subject to potential interference from AM radio. Many other electrical sources (e.g. low voltage lights, heating pumps and speakers) can also cause impulse interference that affects stability. This is one reason for rate adaptive ADSL, so that during periods of noise, an ADSL modem will disconnect and re-negotiate a speed that can be sustained, and is less susceptible to the interference. One thing many people are not aware of is that the time of day is a big factor in the reliability, since during the hours of darkness the interference mentioned above can often be worse. As the nights draw in, people who have had lines that were stable for 6 months may find things become more unreliable.

An ADSL modem disconnecting once or twice a day is probably acceptable to 99% of ADSL users, but when it happens more often, plenty of people have found by using an ADSL faceplate at their BT master socket the effects of noise can be diminished. This is hardly a unique situation to the UK and our old copper network is probably of similar age and quality to that of other countries that use ADSL.

The AR7 problem highlighted appears to be more to do with frequent re-syncs in a short period of time with the modem refusing to connect at a slower, more sensible, speed. With the BT Wholesale Max product, this can result in an increase in the target noise margin, i.e. sacrifice speed for stability.

What is not obvious for those quickly reading up on this issue, is that different modems using the AR7 chipset can actually perform very differently on the same telephone line. We have a number of AR7 based devices and the Netgear DG834G does disconnect a number of times in the evening on a noisy line, while a Solwise SAR-600E and 600EW appear to be highly stable. The line in question is not of the best quality, and it has two master sockets and a star configuration which can mean transient noise can have a great effect on stability.

In summary, some people are seeing issues with some AR7 based kit, but until we have a lot more information, it is hard to draw any firm conclusion. If you have hardware that appears to disconnect a lot, the first thing to do is ensure it is not the telephone wiring in your property before running out to buy a new ADSL modem or router. This can be done by testing your ADSL hardware in the test socket of your BT Master socket. If this is more stable then your extension wiring is having a negative effect on the line. To access the test socket, you must have a new-style split faceplate known as a NTE5. Unscrew the two screws that hold the lower face plate on to the rear, and carefully remove this portion, avoiding disturbance to any wiring connected to it. You should reveal a second socket on the right hand side of the portion still attached attached to the wall, as pictured. This is the test socket.


Click image for a larger version

If you are sure your home wiring is not the issue and things remain unstable, a good course is to borrow some hardware from a friend for a few hours to see if that works better on your line, thus avoiding buying what may be another lemon device. A number of people who have had problems have found that SpeedTouch devices appear to run reliably.

We look forward to more information surfacing over time on this issue. Investigation may reveal that only one particularly DSLAM exhibits the problems with the AR7 chipset, or that a firmware upgrade could tweak performance to an acceptable level. When looking at ADSL hardware over the years we have found things like firmware upgrades can drastically alter how hardware behaves, so those happy to carry out their own upgrades may want to try this to see if it makes any changes.

Comments

Posted by herdwick over 9 years ago
Always pays to try different routers wen there's a problem. I have seen AR7 routers work where nothing else would connect, equally have seen 2wires work where the AR7 wouldn't and vice versa. At home the AR7 Netgear 834 gets me an extra half meg of sync speed. Have had a Netgear 843G replace a very wobbly Zyxel 660 without issue - both have the same chipset. Also had a Speedtouch be stable where a Zyxel was erratic. It's a lottery, so buy plenty of tickets :-)
Posted by chrysalis over 9 years ago
Also about firmwares, speedtough 546v5 and 585v6 have the same chipset but different firmwares. The latter is a lot more stable.
Posted by gromit69 over 9 years ago
Is there a list anywhere of which routers use which chipsets?
Posted by plesbit over 9 years ago
My DG834G disconnects several times most evenings. It is annoying, but not majorly so as it re-syncs far faster than any other router I have seen, and I've seen a few. It also maintains much higher sync speeds than any other router I have tried on the line, again that's a few. I always put the disconnections down to its obsession with incredibly fast sync speeds.
Posted by CARPETBURN over 9 years ago
In my time ive had 2 netgear routers, a dlink, and 2 speedtouch and while like most i have no idea on the chipsets they used ive never really had any issues... Maybe i am just lucky :)
I do agree with gromit69 a list of what chipsets routers use would be useful, maybe this site or one of the other dsl sites could draw something up. Im sure users would appreciate and use it to aid in their router choice.
Posted by jerrymartin over 9 years ago
Luckily I havent had no disconnects with my latest braoadband provider. I had at least 4/5 a day when I was with Tiscali. It didn't help when there is no BT master socket installed (I think the line must have been installed in the house before BT started using the master sockets). The India call centres could no comprehend the fact that I could not test my broadband through the test socket, I didnt have a master socket!!!!!!!!!
Posted by CARPETBURN over 9 years ago
quote"The India call centres could no comprehend the fact that I could not test my broadband through the test socket"

Training does not extend to anything above reading a script and memorising it, thats why ;) lol
Also heres a question ive wondered, is there a single ISP out there which uses indian call centres where the staff actually have any idea when it comes to anything remotely technical?? and if not why do so many ISPs (apart from cost) continue to use them? The mind boggles.
Posted by gedw over 9 years ago
List of DSL chipsets:
http://www.chipweb.de/dsl/index.php?menu=1&level=9
Posted by Fellwalker over 9 years ago
My Netgear DG834G had been connected for 79 hours WAN, 1155 hours LAN, 814 hours WLAN before a power cut yesterday. Now 18 hours without reset. I still get evening speed problems.
BUT ITS NOT THE LINE THAT IS AT FAULT.
BT speed test shows 5500 (5.5Mbs) or so at most times of day or night. BUT real world speed test from yourselves, shows speed down under 1000. http://www.thinkbroadband.com/speedtest/results/id/11934952592292909735.html was this weekend.
I have been on a master socket for 5 years. The issues only arose since i took on the new BT level 3. BT says my connection is good.
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