Slow connection - Cable modem

Question

All the topics discussing slow connection problems seem to include wireless equipment. I use an ordinary cable connection with external modem & 5Mb per second service from my cable company.
About a week ago, surfing different websites became extremely slow.
Loading this page to begin typing my thread took about 20 seconds. The status bar will go to about 30-40% immediately then hang for about 15-20 seconds before fully loading the page. Same with all websites no matter the time of day. The speedcheck gives numbers for downloads - 4.63 and 536.59 for uploads. Clearly, the modem is doing its job.
I emptied the history, cleared cookies but that's all my limited experience allows me to do on my own. Any ideas?

Answer 1

When you used one of the speedtest websites to check throughput, was that before or after clearing the browser's cache? Some bandwidth test sites (most of them, I think) store the results in the browser's cache, and if you forget to clear the cache before re-running the test, you can be temporarily dazzled by the immense increase in throughput! The "4.63" for downloads was Mbps, right? And this problem started in the last week or so, with performance before then being acceptable?
In System Preferences> Network, under the TCP/IP tab, do you have explicit DNS server IP numbers entered or is the box left blank? Since you're getting partial page loads before stalling, I don't think it's a cse of an ISP telling users to enter explicit IP DNS numbers, then changing their DNS servers without notice (that happened to me), but if you do have explicit DNS numbers in that box, note the numbers then try clearing the box to see if that makes a difference (a blank DNS server box pushes DNS request back to the ISP's servers, which should always respond with up-to-date server links).
Another unlikely-but-possible scenario (which also happened to me) is if your ISP changed their cable modem server hardware (e.g. from DOCSIS 1.0 to DOCSIS 2.0) without bothering to notify their customers. That caused random disconnects and inexplicable stalls seemingly at random when my ISP pulled that stunt. Calls to the ISP's national support center were no help; a chance remark by s counter worker while in the brick-and-mortar local cable company office elicited information about the change. That you bought a brand-new modem suggests your modem should be fully compliant with any current server hardware. However, there are known to be some incompatible and worse some partially-compatible modem brands that don't work properly under OS X --- even different model numbers in the same modem family (e.g. Motorola Surfboard) make a difference.
What manufacturer and model cable modem are you using? Try calling your cable company's local office and ask them when make/model modems are they handing out to new customers who rent their modems, also ask if the local people are aware of any recent server hardware or local cabling changes (they haven't been tearing up your street to install FiOS, have they?). The ISP's support website should have a list, which should also be available from the local cable office, of modem manufactures/brands that they've approved as compatible; while that list is invariably Windows-centric, it's still a good idea to stick to those makes and models.
If the ISP has tweaked things recently, you may be able to use the modem you already have by tweaking the MTU (maximum transmission unit) value from the usual value of 1500 to say 1420. You can do that manually in System Preferences> Network> Show: Built-in Ethernet> Ethernet tab --> Configure: manually (advanced) and changing the Maximum Packet Size (MTU) value.
IE is a dog under any conditions; try using Firefox instead as an independent check on Safari. There have been the usual reports of some users having problems with the new 2.0 release of Firefox (and others reporting wonderful things about it); you can try the stable 1.5.0.8 release from Mozilla's Firefox releases archive.