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Author Topic: PC Pro Feb 2008 article  (Read 17689 times)

jaypeecee

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PC Pro Feb 2008 article
« on: December 21, 2007, 05:58:24 PM »

Hi Folks,

I've just read an interesting article in the latest (Feb 2008!) copy of PC Pro magazine. In the article, the author starts out by saying that he has the all-too-familiar line disconnect/loss of sync problem. After much investigation, he concludes that the problem is caused by three factors. Firstly, the use of a TI AR7 chipset-based router. The second factor is to be using an ADSL Max-powered service and the third ingredient is for some external factor that increases the line noise.

What I find interesting about this article is that it conflicts with my experience. I'm now using the Netgear DG834G v3 modem/router, which is based on the AR7 chipset. I chose it because the Kitz site specifically states that it performs well under low noise margin conditions. And does it perform well!! I've not had a single disconnect since I bought it three weeks ago. My noise margin is never in excess of 12dB. So, that takes care of two of the factors described in the PC Pro article. As for the ADSL Max service, I'm not sure if that's what I'm on. Because of my distance from the exchange, BT said the best download speed I could expect was 2Mbps. I get 1.9Mbps so I can't complain.  Therefore, my question is - why does there appear to be a difference in performance between the PC Pro article and my experience with an AR7-based modem/router? Is it to do with the ADSL Max service?

JPC
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roseway

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Re: PC Pro Feb 2008 article
« Reply #1 on: December 21, 2007, 07:40:17 PM »

I think the truth is that there are numerous possible reasons why a particular line may be unstable, and the author of that article is guilty of making too many assumptions based on his own personal experience. We've seen numerous reports from people saying that the DG834 with the AR7 chipset has proved to be the most stable router for them, because it holds sync down to very low noise margins. But there are others who say that it has critical flaws which make it a bad choice.

There's no single single router which is the best choice for everyone. As it happens, for me the Speedtouch ST576 is the best router out of many which I've tried, but I continue to suggest the DG834 as a good option for difficult lines.

It's certainly true that, for some people, going over to ADSL Max has destabilised what was previously a satisfactory fixed-speed connection. But for most people it gives higher speeds and still adequate stability. So once again there's no single answer to suit everyone.
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oldfogy

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Re: PC Pro Feb 2008 article
« Reply #2 on: December 22, 2007, 01:48:24 AM »


But there are others who say that it has critical flaws which make it a bad choice.

And they are most likely the people complaining about it.
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farmergiles

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Re: PC Pro Feb 2008 article
« Reply #3 on: December 22, 2007, 10:25:35 AM »

I think the DG834Gv3 is a very good router. It would sometimes go from 6db right down to zero and stilll hold the line.My DSLAM is TI and it seemed to work fine with it most of the time.
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mr_chris

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Re: PC Pro Feb 2008 article
« Reply #4 on: December 22, 2007, 04:54:08 PM »

I think we are going to see more and more cases of people jumping on the AR7 bandwagon since Zen made that announcement about it.

OK, so there may be some factor relating to the AR7, certain types of line interference, whether the line is interleaved or not, what DSLAM is in the exchange, etc.. that under SOME circumstances means the AR7 does have a problem.

But think about the number of DG834 series routers and countless others based on the AR7 that have been sold... if every single one of those had a problem as Zen were basically alluding to, don't you think we'd have heard a tiny bit more in the way of complaints??!

It does annoy me when people supposedly in a position of trust and authority (i.e. Zen being a very well respected ISP in the UK) put out what is basically little short of scaremongery.

Just to add, my Netgear stayed synced on ADSL Max for many weeks at a time. It's likely the article's author has a problem with some bad external interference and is factoring the Netgear into the blame when it probably is nothing whatsoever to do with it. I bet he didn't try another router first!
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Chris

jaypeecee

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Re: PC Pro Feb 2008 article
« Reply #5 on: December 23, 2007, 04:54:37 PM »

mr_chris,

Far be it for me to defend the article's author as what he was saying conflicts entirely with my experience using the AR7-based Netgear DG834G v3. With reference to your point about 'I bet he didn't try another router first!', in fact he did - a SpeedTouch 546 wired ADSL2+ router - and this put an end to the line drops and re-syncs. I've just discovered that the article to which I'm referring can be found onlne at http://www.pcpro.co.uk/realworld/144378/route-to-ruin.html.

Out of interest, I was using a BT Voyager 2091 prior to the Netgear and that's why I made the change. The Voyager was losing sync every few minutes and it seemed to coincide with the wetter weather we have been having since September this year. Does anyone know what modem chipset is inside the Voyager?

Finally, it looks as though I'm on an ADSL Max line.

JPC
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guest

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Re: PC Pro Feb 2008 article
« Reply #6 on: December 23, 2007, 07:14:08 PM »

I think there have been some microcode updates* applied - some more effective than others.

I understand that Zyxel took a decision that the chipset was so flawed that it was uneconomical to support - I have a P2602HW which has the AR7 and that got binned VERY fast for the top of the range router (£150 or so) which they sold at the time.

Netgear obviously felt differently. Zyxel (Europe) development/support is in Denmark/Sweden, Netgear is a US company (as is TI) who sell shedloads of modem/routers to US ISPs - I'm not sure if that was a factor or not.

*this is usually where the processor has a hardware design flaw and so there's a patch applied. On AMD cpus it will be a s/w patch that has to be applied each time the machine boots - or more accurately AFTER the cpu boots; on Intel (recent) cpus its possible to patch the processor (sort of) directly.
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jaypeecee

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Re: PC Pro Feb 2008 article
« Reply #7 on: December 23, 2007, 07:24:29 PM »

I've answered my own question about the chipset in the BT Voyager 2091. Apparently, it's the Broadcom BCM6348. Having read more stuff on the net, I'm now of the view that there's a lot of opinion out there and not a lot of fact. So, I'll continue to follow the AR7 debate with interest.

In the meantime, I'm delighted with my Netgear DG834G v3 - does just what it says on the tin!

JPC
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kitz

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Re: PC Pro Feb 2008 article
« Reply #8 on: December 23, 2007, 10:37:56 PM »

Hi

Theres a couple of other threads on this forum where we have dicussed the "AR7 chipset issue"  announcement by Zen. 
Since then, I have always asserted that although there may be something in the AR7 chipset theory.. I do believe that there is some other element behind the true cause.
There are far too many users who have reported that the dg834g has helped their connection.
 
Ive also been in touch with one of the guys from Zen about thishad some correspondence with one of the guys from Zen about this, there are also many more people who do not believe it is soley the AR7 chipset.  Even Zen admit it is not the only cause.

If it was then Im sure there would be a heck of a lot more complaints about it - particulary since the netgear router is one of the most common routers out there.  Without a doubt the Netgear does peform better on many lines than some other routers. - The old zyxel could be pretty carp anyhow, and there are some users who would have problems with a zyxel yet be fine when they put a netgear on the line.


>> So, I'll continue to follow the AR7 debate with interest.

Me too.
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mr_chris

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Re: PC Pro Feb 2008 article
« Reply #9 on: December 23, 2007, 11:52:45 PM »

@ JPC - my little rant wasn't directed at you, in fact reading back it was a little bit more of a rant than I intended at the time!!
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Chris

kitz

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Re: PC Pro Feb 2008 article
« Reply #10 on: December 23, 2007, 11:55:59 PM »

naw I think you may be right - particulary
"I think we are going to see more and more cases of people jumping on the AR7 bandwagon"

Ive already seen people accuse their router without checking out the more obvious causes - Ive even seen someone blame the netgear - but it was the dg834gt which doesnt have the ar7 chipset anyhow. :/
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jaypeecee

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Re: PC Pro Feb 2008 article
« Reply #11 on: December 24, 2007, 10:40:31 AM »

@ JPC - my little rant wasn't directed at you, in fact reading back it was a little bit more of a rant than I intended at the time!!

Have no fear, mr_chris. I didn't perceive your comments as directed at me, nor did I see them as a 'rant'. You were simply making some good points.
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mr_chris

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Re: PC Pro Feb 2008 article
« Reply #12 on: December 24, 2007, 01:51:34 PM »

Good.. glad about that :)

I'd like to be able to do a bit more investigating on the AR7 problem. I have a feeling it's to do with when the line is interleaved, too. My Netgear wasn't as stable when my line was interleaved, and it didn't hold sync as well as when I got it put back on fast path, so perhaps that is an issue. I still think Zen should have performed some investigations (they are in a good position to do so, or they should be!) before releasing such a sweeping statement.

They should have started small i.e. "it affects AR7 with such-and-such a DSLAM and such-and-such a line profile" and allowed others to expand on it, rather than saying all AR7s are bad, and then everyone trying to cut through the noise to determine exactly under what circumstances!

So the PC Pro guy did try another router... did he say by any chance what make of DSLAM was at the exchange or whether he was on Interleaved or not? Those are the sorts of things that need to determine exactly what the flaw with the AR7 is.
« Last Edit: December 24, 2007, 01:54:58 PM by mr_chris »
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Chris

Azzaka

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Re: PC Pro Feb 2008 article
« Reply #13 on: December 28, 2007, 10:16:38 AM »

Good.. glad about that :)

I'd like to be able to do a bit more investigating on the AR7 problem. I have a feeling it's to do with when the line is interleaved, too. My Netgear wasn't as stable when my line was interleaved, and it didn't hold sync as well as when I got it put back on fast path, so perhaps that is an issue. I still think Zen should have performed some investigations (they are in a good position to do so, or they should be!) before releasing such a sweeping statement.

They should have started small i.e. "it affects AR7 with such-and-such a DSLAM and such-and-such a line profile" and allowed others to expand on it, rather than saying all AR7s are bad, and then everyone trying to cut through the noise to determine exactly under what circumstances!

So the PC Pro guy did try another router... did he say by any chance what make of DSLAM was at the exchange or whether he was on Interleaved or not? Those are the sorts of things that need to determine exactly what the flaw with the AR7 is.

The thing is, it doesn't affect such-and-such a DSLam nor a line profile. What it does effect is a DSL Max line that has a fluctuating SNR. Whilst it is still being looked into, there are other reasons to suggest that the problem is also related to interleaving as this has also been seen to cause the problem.(Kitz was the first one to relate this issue to me)

As for Netgear not doing anything about it, I have been speaking with them at length and although we have not found a solution we are still testing and working with both Infineon (the makers of the AR7 chipset) and BT to find a solution to the ongoing issue.

There was a large discussion about this matter on the thinkbroadband forum and I am sure it will be discussed here at length as well. As for releasing such a sweeping statement, Zen didn't release it, The Register did. Phil D.Long was misquoted throughout that article.

Quote
So the PC Pro guy did try another router... did he say by any chance what make of DSLAM was at the exchange or whether he was on Interleaved or not? Those are the sorts of things that need to determine exactly what the flaw with the AR7 is.

The DSLam does not make a difference at all. The modem code and the firmware does however. For now we do not have an answer, but we are getting closer to finding a way to keep the same interoperability of the AR7 chipset with the stability of the Broadcom.
« Last Edit: December 28, 2007, 10:21:22 AM by Azzaka »
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kitz

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Re: PC Pro Feb 2008 article
« Reply #14 on: December 28, 2007, 05:23:58 PM »

One thing that does occur to me with the Netgear (bear in mind I'm theorising here and dont have access to the large resource of differing types of lines/dslams like Zen does).. and Im just chucking a few ideas into the hat... and I could be talking rubbish.

... but the netgear is reknown for holding on to low snr lines when most other routers will have dropped the connection.
Quite often once SNR gets too low then errors start being introduced on the line.  For a non-interleaved line obviously these will be CRC/HEC errors.  For an interleaved line you can get tons of FEC errors... could there be something in that?

I still strongly believe there is another factor into this problem, but finding out what this is, is going to be the hard part.

Without a doubt some routers do perform better than others on lines.. there are some routers I would avoid... the Netgear DG834x isnt one of those.  There really is just too many instances Ive either seen first hand or had reported to me that that particular router has helped stabilise long lines.

It could just be that the ST routers are better than say the Netgear ones.  Theres also many many rumours that "pairing" the dslam + CPE chipsets do seem to provide better results.

>> The Register did. Phil D.Long was misquoted throughout that article.

Hmmm  yes on reflection that does make some sense, it wouldnt be the first time.
Phil does carry a certain amount of respect and knows his stuff..  hence why some of us were surprised at such a "broad sweeping" statement.

I havent been on the zen own forums recently but perhaps an updated statement by Phil on "Home Turf" could perhaps clarify some issues.

>> The DSLam does not make a difference at all.
Interesting - thanks for that.. I had wondered if there was something in the dslam/MSAN thing.

>> the firmware does however

Yes - which could also be why IMHO say the Netgears are better than say the old zyxels, which I'd seen perform not as well as others.
DSLmax pushes most lines to their limits, and the "roots" of most firmware goes back to pre-max days.


>> For now we do not have an answer, but we are getting closer to finding a way to keep the same interoperability of the AR7 chipset with the stability of the Broadcom.

Thanks for that.
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