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'Ware Speed Test Accuracy

lorisarvendu
Grafter
Posts: 333
Registered: 26-08-2007

'Ware Speed Test Accuracy

We had a couple of power cuts in the town on Saturday.  Ever wary of anything that may jeopardise my pristine FTTC download speed (ha ha) I did a speed test...and found to my horror that speedtest.net was reporting my download rate to be 44.66Mbps instead of the usual 67-72!
Luckily I have more then 1 PC in the house, which makes it handy to compare notes. Speedtest.net on my Linux box gave me a figure of 72, so I began to suspect my Windows PC of having some kind of bottleneck. 
However I then downloaded a DVD ISO of Slackware 14, which came down at approximately 8.5MBytes per second.  Hang on...that works out at round 60-70Mbps. I ran speedtest.net again.  44.
This morning I've done the same again, and got the same result.  Speedtest.net only gives me 44Mbps on this PC.  However the BT Speedtester reports about 67Mbps, while MyBroadbandSpeed.co.uk gives 40.6Mbps
For some reason (and on that PC only) different speed testers are giving wildly different results. 
-Dave
A tortoise? What's that?
You know what a turtle is? Same thing.
10 REPLIES
Community Veteran
Posts: 4,826
Thanks: 117
Fixes: 24
Registered: 14-07-2009

Re: 'Ware Speed Test Accuracy

Which version of Windows does your PC run?
lorisarvendu
Grafter
Posts: 333
Registered: 26-08-2007

Re: 'Ware Speed Test Accuracy

XP Pro SP3.
A tortoise? What's that?
You know what a turtle is? Same thing.
Community Veteran
Posts: 26,656
Thanks: 883
Fixes: 10
Registered: 10-04-2007

Re: 'Ware Speed Test Accuracy

Your RWIN is probably too small. Have you tried tweaking your TCPIP settings?
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
lorisarvendu
Grafter
Posts: 333
Registered: 26-08-2007

Re: 'Ware Speed Test Accuracy

Yes I have actually.  I used TCPOptimiser some time ago.  The odd thing is that it's only certain speedtesters that give eroneous results.  Real-world downloading is absolutely fine, and conforms to what the BT Speedtester says my line is anyway.
RWIN is 2090880
-Dave
A tortoise? What's that?
You know what a turtle is? Same thing.
Community Veteran
Posts: 26,656
Thanks: 883
Fixes: 10
Registered: 10-04-2007

Re: 'Ware Speed Test Accuracy

Have you checked if different speedtest.net servers give different results (you need to try those around London as they are the nearest to you by wire).
MyBroadbandSpeed uses the same Ookla engine as speedtest.net.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
kmilburn
Grafter
Posts: 902
Thanks: 2
Registered: 30-07-2007

Re: 'Ware Speed Test Accuracy

From experience, it appears that not all the speedtest.net servers are capable of 80mbps so you could be maxing out the other end, not yours!
lorisarvendu
Grafter
Posts: 333
Registered: 26-08-2007

Re: 'Ware Speed Test Accuracy

Can't see how it's the speedtest.net servers as I get full results when I run it from Linux.
A tortoise? What's that?
You know what a turtle is? Same thing.
Community Veteran
Posts: 26,656
Thanks: 883
Fixes: 10
Registered: 10-04-2007

Re: 'Ware Speed Test Accuracy

What MTU do you have set on the PC and on the router?
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
kmilburn
Grafter
Posts: 902
Thanks: 2
Registered: 30-07-2007

Re: 'Ware Speed Test Accuracy

If you 'use begin' to test the speed, it selects the best server based on ping (or so it says),  so tests on two machines could have resulted in selection of a different server,  with a different result.
If you want to guarantee consistency, it's better to pick the server manually.
lorisarvendu
Grafter
Posts: 333
Registered: 26-08-2007

Re: 'Ware Speed Test Accuracy

Well now. It's picking London automatically anyway, but if I run it in quick succession I'm getting figures all over the place now.  56 one minute, 73 the next.  66 the next.  Time to reinstall Windows? lol
A tortoise? What's that?
You know what a turtle is? Same thing.