Broadband speed test

[SlimJim]

I'm not sure where to place this question so please excuse me if it is in the wrong place.

I have two desktop computers connected to the same modem. The first is a fairly old Fujitsu Siemen Scaleo [Pentium 4 (2.4Ghz), 768Mb memory, XPHome SP2] cable connected via a powerline extender. The second is a more modern Packard Bell iMedia [Intel Core 2 Quad Q6600 (2.4Ghz), 3Gb memory, Vista Home Premium] connected wirelessly via a USB adapter.

Today I ran the broadband speed test from www.speedtest.net on both computers, not simultaneously, but within a few seconds of one completing I ran the other. The upload speeds were almost idential at 372Kbs but the download speeds were vastly different with the faster computer registering around 6800 Kbs and the slower registering around 4800Kbs.

Can anyone throw some light on this? I naively thought that broadband speed was a test of the connection speed only (i.e. modem via ISP to server) and independent of the computer connected. Clearly this is not the case here.

 

[SlimJim]

Sorry - more information. I didn't realise that speedtest had more information.

It turns out that the difference is in something called latency. The faster figures had a latency of 79ms whereas the slower figures had latency of 105ms.

Am I right in assuming that this is affected by computer speed?

 

[Ian]

That's an interesting setup - how does the powerline extender connect to the modem?

The latency figures are the "ping" times to the test server (i.e. the time it takes for information to get to and from the test machine). Cabled modems are often faster at this, as wireless cards often add extra latency, slowing down this time slightly.

It looks like one of the PC connection methods (I'm guessing the powerline adapter) isn't as fast as the other. So although your modem might be able to receive data at 6800kbps, one of the adapters can't get that data to the PC as fast.

As the speed test runs on a specific PC, it has to take into account the whole connection (PC > Modem > ISP > Test Server). In this case, the 2000kbps difference seems to occur between the different PC > Modem stages.

 

[SlimJim]

That's an interesting setup - how does the powerline extender connect to the modem?

...SNIP...

As the speed test runs on a specific PC, it has to take into account the whole connection (PC > Modem > ISP > Test Server). In this case, the 2000kbps difference seems to occur between the different PC > Modem stages.

Thanks for the response.

I have a short cable from the modem (wireless + 4 ports) to the first powerline adapter and then (in another room) a fairly long cable (about 7m) from the powerline adapter into the older computer. The setup is like this because I have no telephone socket in the computer room and a wife with strong objections to cables running through walls etc.

I have not come across any suggestions that the powerline adapter introduces significant delays and unfortunately it is too complicated to disconnect everything and move the computer nearer to the modem to test it on a direct ethernet connection to the modem.

I think I was a bit shocked at the differences because I thought that the wireless connection might be slowing down the newer computer, apparently not. Even switching the connections between computers is non-trivial as most of my cabling is "tidily" locked down. However, if I get an hour or so with nothing else to do I might have a shot at it.

 

[SlimJim]

Sorry to keep hogging this thread but I am finding this fascinating because of the presentation of results at speedtest.

I have just completed another round of tests, without altering anything!!, and thoughout the morning the latency of my wired connection is steadily decreasing, it has dropped from 109ms to 89ms with a corresponding increase in download speed from around 4600 to around 5300. The wireless connection has stayed pretty well constant with latency 79ms or 80ms and download speeds up to a max of around 6800.

If only I could work out why the latency is dropping? I might be able to achieve some permanent improvements.

 

[Ian]

Ping times do change slightly all the time, depending on traffic usage etc... If you go to the command prompt by typing in "cmd" from the run menu, and then try "ping bbc.co.uk" it will tell you the ping times to the BBC website. I get different ones each time

As it's the powerline adapter doing this, I suspect it's just to do with the way the technology works. As the signal piggybacks onto the back of your mains AC it's never going to be quite as steady as another transmission system. I wouldn't worry about it personally, but if you do want to get round it you could always buy another wireless network adapter for a tenner.