Why is the ethernet connection 4.5 Mbps slow on my iMac when should be 20?

I've seen routers that will do this before. In these cases, you could plug a computer directly into the modem and get 15 Mbits and then plug the router into the modem and the computer into the router and only get 5 Mbits.

Not sure this really helps much, but I would try testing with and without the router in the equation to see if you can at least isolate the problem.

I am having the same issue except mine is stuck at @ 5Mbps. I live in Florida and use Comcast Business Class with an SMC 8104 modem. I have been all over the internet today trying to figure out why this is happening. Does not matter if I am going straight through the modem or my Airport I get about the same speed...all the while my Lenovo laptop get's 13Mbps - 15Mbps virtually every time...

Please post if you find something out.

I have the same problem on my wifi network (modem/router and Linksys g as wireless access point).

Other devices (netbook, iPhone, Xbox360) are fine, but my iMac won't reach full speed (10 Mbit). Most of the times it gets 2-4 Mbit/s and sometimes it doesn't even get 1 Mbit/s. This iMac is brand-new, just got it a week ago and I'm really sad/frustrated that my very first iMac is giving me grief like this.

My new 27" imac is really slow as well. I am able to browse pages, but trying to do any kind of download or even system updates starts out fast and then tapers down to nothing at all. Eventually a system update will fail and if I restart the download it does a bit more and then stops again....

My network is ethernet cable into switch out to cable modem on the internet. My PCs are not having any problems at all....

Does anyone know what is going on with this?

Tony

Same issue as others. Bought an 27" core i7 iMac with 8GB ram in early April 2010. Works fine except for the internet speed, which ranges between 3 and 5 megs whether using wireless or turning off wireless and going through ethernet cable directly to the airport extreme (no intermediary hub or switch).

At the same time, my 2006 MacBook Pro, with 3GB ram, will get 15 to 23 megs using wireless. It's sitting right next to the iMac (or even twenty feet further away from the airport extreme) when it achieves these speeds.

After 10 to 15 tests (using both flash and java speed tests at dslreports.com), the results have been unfailingly consistent. The iMac is 3 to 5 megs. The MacBook Pro gets 15 to 23.

The results are the same even when the iMac is running nothing but Safari and the MacBook is running Safari, Excel, Word, VMware, Entourage and other programs. Both machines are running 10.6.3.

It sounds a lot like the ethernet port is not configured correctly, either in your network preferences or by the default settings used by Mac OS X.

If you go into Network system preference and the Ethernet connection, click Advanced and choose the Ethernet section, just check that the speed is set to 1000baseT, Duplex is full-duplex, flow control, MTU Standard (1500) (this is for a UK setup, not sure if it would be any different in other countries).

Another thing to make sure of is that you are using a fully connected ethernet patch lead, if you look at the clear plug you should be able to see that all of the wires are present (there are no unconnected pins) and that there are no crossed wires either - the colours should match at both ends of the cable with the plugs positioned side by side.

Message was edited by: Jonathan Mortimer

have you tried turning off your bluetooth....i had a problem with the bluetooth disrupting my wifi signal it would get so slow when i turn on the bluetooth and it would speedup like a rocket when i turn it off....i haven't solve the problem so if anyone could help me......

I cannot turn off the bluetooth-my keyboard and mouse will not function....

This network performance issue is ridiculous....Has anyone reported anything to Apple on this?

just use standard windows keyboard and mouse it should work fine...theres so many problems about this network performance issue posted so far no one has tried this before so i would like to know if the problem really is the bluetooth if so than all the new mac will have this problem....

I have a brand new i5 iMac, nothing wrong with my network / broadband speed here in the UK (I am with BT). I use the default Apple Bluetooth keyboard and magic mouse.

Has anyone had any luck with any of the possible solutions offered up here?

As far as I can tell, there have been no definitive answers, just different things to try.

Changing the ethernet settings did nothing for me.

I'm going to try a different ethernet cable tonight, but I doubt that's the problem.

maybe it's just my imac or the router...someone suggest changing the router channel so far it didn't work..i use d-link dir-300 wireless router it uses 13 channels and the BT interfere with all the channels...does anybody has other suggestion???

I have tried new cables etc....
I am not using the wireless connection for this.

I am looking into see if it is a NATing problem with my firewall, I just do not understand why my PCs work fine on the same network....

Very confused....

I turned airport off and tried a new ethernet cable directly to the airport extreme. Still no luck. Speeds on the new iMac are a quarter of what they are on a 3 year old MacBook Pro connected by the same cable to the same airport and test minutes apart. Have done dozens of tests and the results have always been the same.