Ok, so recently I bought two Power Macs (G4 MDD and Quicksilver) on eBay as I am trying to go for some iOS development later on and some other stuff.
I have been too used to PCs and when I stare at a Mac I kind of have no idea what I am doing.

So after some basic tutorials I installed Leopard on the MDD.

Works PERFECT, except two issues.

First issue - Onboard Ethernet doesn't work at all.

All it shows is cable unplugged, both the Ethernet cable and router work flawlessly, done many PC installs on it and nothing ever was wrong with it. Tested the cable and reset my Router and same thing.
What I tried to do was reset the location and add back an ethernet setting, but still I get "Cable Unplugged". So I added a Realtek RTL8139 which works fine, however -
Second issue - Using the Realtek PCI card, I have a horrible download speed, updates have been going for around 2 hours downloading, it's so slow. Through Safari, I am getting around 10 - 15KB/S download. It's not my internet/ISP, I am not over my peak limit, my main PC is connected and works fine.

So, that's the first one.

Next, the Powermac Quicksilver.

Installed Tiger on it, as usual, works perfectly fine, however, Ethernet doesn't work as well!
Just "Cable Unplugged". That's it, tried locations and all that and nothing.
Then, I added the PCI ethernet card, and we have slow Download speeds.
I then realized that on the Quicksilver, the actual RJ45 port is quite loose and to get it working I have to fiddle around with it, moving it side to side then it works -.-

I have tried googling my issues, and most people are saying that it's just a configuration error. However, I have another Powermac (Sawtooth), that, once I installed Tiger on it, I had no issues with ethernet whatsoever.

I realize this is most likely a hardware error, but the MDDs RJ45 port looks physically fine, I don't see any missing pins or bent pins or anything, so not quite sure.
But still why is it so slow downloading, using PCI ethernet cards for older PCs work perfect, just with Macs, maybe compatibility issue or something. I am only assuming as I have no idea how to fully use a Mac yet

If anyone can suggest me something, that would be great. (Don't think I need to list specs)

First thing I thought of was Drivers, I need drivers! But, that's not quite the case

Thanks heaps.

Hi and welcome,

all very strange, I'd try another ethernet cable first, make sure it's not a cross-over cable. You might have to remove the motherboard (on both?), and resolder the RJ45 connector to get a reliable connection.

The Realtek 8139 cards mostly work "out of the box", but some are better than others. They are the cheapest network cards around. I did manage to find a replacement Realtek .kext for the 81xx cards here you could try:

RTL81xx OS X Driver [Lnx2Mac's Blog]

JB