[rod.torr]

I have a bunch of Mac's & Pc's networked on a Lan, all these machines have very good ethernet throughput speeds (whether they have 100 or 1000 T base ethernet adaptors) but my iMac G5 is extremely poor @ transferring and receiving files, at around 1 megabyte every couple of seconds.
I have checked/swapped/changed all cabling etc with other machines and I instantly get around 10 Megabytes per second or more.
I have gone into system prefs/network/ethernet/ and manually configured the ethernet adaptor (100 base T, full duplex) and nine time out of ten this makes no difference.
If I do a lot of jiggery pockery as well (logging in and out of users, cache cleaning, permissions cleaning etc) then sometimes, occasionally, I might get full throughput speed, but his is always temporary (half a day max so far) and never last's for very long, yet when the network speed slows down, this can last for day's, or indifferently if I do not do any fiddling around.

[rod.torr]

I have since been told by Apple Tech Support (online chat) that the ethernet adaptor in the imac G5 defaults to 10 base T, not 100, and that you have to set it manualy (in system prefs/networking/ethernet/) to run at 100 base T; which I have done many time now with no permanent improvement.
Can this be true? Also this machine is plugged in to a swicth on a 100/1000 T base port, should I cahnge it to a 10/100 base T port, would/should this make a differnce?

[larkost]

Two things:

The ethernet spec says that you default to 10 base T simplex if auto-negotiation fails, so this is the correct behavior, not that many other vendors follow it... Also if the port is set to a fixed speed but does not have it's duplex set (must be fixed, auto is not a valid option in this case), Apple once again follows the spec and goes to simplex. However, there are a number of devices which break the spec and try to go duplex in this case, causing problems. -- make sure that the port is either set to full auto, or exactly set as the iMac is set... speed and simplex/duplex.

The second problem could be that you have spanning tree set on that port. This should never be set on a client port (only to another router that actively supports it), but many routers ship with it enabled on some ports. This has been an intermittent sensitivity on Apples, and once again is a case of Apple closely following the spec. A uplink port (and it sounds like that is what you are using) is more likely to have this turned on.

[rod.torr]

Thanx for replying, really appreciate it, in the end I just changed the iMac to another port on the switch (10/100) works fine now on auto at either end.

[ghporter]

I'm glad that you got things working and in the process learned about your switch's "substandard" port. It's also a lesson; when you changed all the cables around, the next step should have been to see if the same problem occurred on a different port, and when you didn't say explicitly that you'd done that, I should have asked.

While in retrospect it will seem obvious to you, it's an important part of troubleshooting that's easy to skip. You have to test all the possibilities to make sure the problem is what you think it is.

[larkost]

ghporter: "substandard" is not the right word at all. It is probably a configuration issue with a port that is supposed by the manufacturer to be an uplink port... and the fact that many vendors have gone Microsoft's way and ignored parts of the ethernet spec... in ways that actually make sense, but still are out of spec, and tend to break machines that are in spec...

It would have been a good idea to check the port, but your categorization of the port was probably dead wrong.