Why is my internet download speed bumpy?

May 12, 2012 10:25 AM

When I do a speed test on my cable modem why do the results look different in safe mode?

While trouble shooting my cable modem sloooooowwww down issue I noticed that while checking my bandwidth speeds in safe mode the download portion of the test is flawless. A very nice and smooth progression of the meter so to speak. When not in safe mode the download is bumpy. In other words the meter jumps around although the speed results are the same. The upload portion of the tests seem identical.

I am using the Speakeasy and the Charter Communications speed tests.

Nothing is different equipment wise and no programs are running when I check the task manager.

Windows 7
Motorola docsis 3.0 6120
Cat 5 - not wireless
ISP is Charter Communications

My slow down problem seems to be fixed (um...er... utorrent on startup no more!) but why isn't my download looking as pretty as when I am in safe mode?

posted by snowjoe to Computers & Internet (8 answers total)

Probably an artifact caused by multitasking. In safe mode, a lot of normal background tasks are not running.

I suspect you have a single core CPU, not dual- or multi-core, right?
posted by Chocolate Pickle at 10:57 AM on May 12, 2012

Response by poster: OP here - my processor is AMD Phenom ll x2 555 - dual core I believe.

Task manager definitely says that nothing else is working. If something were going on in the background wouldn't task manager tell me so?
posted by snowjoe at 1:00 PM on May 12, 2012

Windows runs lots of processes, or services, in the background. You will find these on the Processes tab of task manager, along with applications you have manually started. One of the services that may not start in safe mode is your anti-virus program, which is likely set to scan everything being downloaded. This of course could affect the rate at which your browser receives the data from the speed test. I do not know for certain that this is your issue, but it is where I would begin my own search for an answer.
posted by dave*p at 1:14 PM on May 12, 2012

If you type "msconfig" in your search bar you will get a list of services that are running. They run in the background (and probably also show up in the processes tab of Task Manager as dave*p said). Most of them don't load up during Safe Mode.

Honestly if you dont have any slow down issues now and your nonSafe mode speed tests seem normal, you are probably good to go and it is just caused by those normal processes.
posted by Twain Device at 3:08 PM on May 12, 2012

Does Windows fall back to generic network interface drivers and/or conservative settings? I could easily imagine that in safe mode Windows would use the bog standard "works with any NIC" driver with conservative settings. Since cable speeds are nowhere even close to the limits of any modern card you would still get the full speed, but it might be using small buffers that return small chunks of data at a consistent rate, and use conservative TCP slow start. This would give the impression of the speed smoothly climbing up to a maximum and staying there. In normal mode, Windows would use the card specific drivers and configure aggressive settings for buffer size and TCP tuning. This would cause data to arrive in larger bursts at less frequent intervals. Any speed test program that was calculating on data received at the application layer would bounce around the max speed. A better speed test program that was polling the card directly would count packets as they were received. Fast ramp up on TCP might also cause speed to flutter about. Either way the final speed would be the same. You can think about it like a person jogging compared to a person half-waling, half-running the same mile and starting and finishing at the same time.

Unless it's other processes interrupting the flow, or you have some hidden new Windows virus.
posted by zengargoyle at 4:01 PM on May 12, 2012

Windows does not use generic NIC drivers in Safe Mode.
posted by dave*p at 5:44 PM on May 12, 2012

If you're running Norton Antivirus, uninstall that son-of-a-bitch and install Microsoft Security Essentials instead. Norton Antivirus has become legendary as a source of all manner of "Why doesn't my computer run fast anymore?" complaints, including internet speed issues.

Norton Antivirus is one of the programs that doesn't run when you're in safe mode.
posted by Chocolate Pickle at 5:51 PM on May 12, 2012

What's the overall speed for each of the tests? Is there a graph the speed at each point of the test? I'd be curious to see how [un]steady the download is on safe/non-safe mode - is it just natural internet fluctuations, or something else.
posted by Sonic_Molson at 10:57 PM on May 12, 2012