Explaining speed test results

I'm on PN's 40/20 product and my line syncs at better than 79/19. This picture is the TBB speed test result. The first set of figures seem OK at 37Mb/s but why does the x6 download give a speed that's so much lower?

http://www.thinkbroadband.com/speedtest/button/14471...

XPsp3, wired ethernet, TP-Link W9980 modem/router.

What does http://labs.thinkbroadband.com/speedtest show?

No precise answer, but most likely is that when doing six downloads at once something finds it is struggling, or the ISP is giving priority to one port while not giving priority to HTTP traffic.

26.5 down, 18 up

So either a PC/flash cpu load issue or traffic management fun

Just tried on another PC. A laptop running Vista. Again wired ethernet.

37.6 up, 14.1 down on the main speed test

Problems with flash when trying to run the alternate test

Managed to sort out flash on the laptop. It's quite a slow old machine, certainly a lot slower than the desktop on which I'm doing the first set of tests.Neither is young. THe desktop is only a Quad Intel CPU Q6600 at 2.4GHz with 3GB of RAM but it always feels fast and responsive.

Anyway, with flash on the laptop the alternate speed test gives 37.7Mb/s on both download tests and 18.5 up.

Conclusion: There's something odd about the way my main desktop is handling multiple simultaneous downloads. Or possibly with FIrefox, though I'm using Firefox on both machines.

http://www.thinkbroadband.com/speedtest/results.html...
http://www.thinkbroadband.com/speedtest/results.html...
http://www.thinkbroadband.com/speedtest/results.html...

Three people all with very different behaviours, one is lucky and enjoying FTTP

With the new version that does not need flash...and filtered to show Firefox only
http://www.thinkbroadband.com/speedtest/results.html...
http://www.thinkbroadband.com/speedtest/results.html...
http://www.thinkbroadband.com/speedtest/results.html...