Slow file transfer - ethernet + firewire issue?

Question

Here's the setup -
Win98PC > ethernet (direct cable connection) > iMac G5 > Lacie d2 FW drive
Connection (100BaseT) works, logins work fine, browsing folders & files is fine. But when I transfer files from the WinPC to the Lacie drive through the iMac G5 it is unbelievably slow. Same thing if I use one of my other Macs in place of the WinPC, so it looks like a network or iMacG5 issue, not a WinPC issue.
On the other hand, if I use Airport to connect a WinPC, eMac or MacBook to the iMacG5, the file transfers are blindingly fast.
Is this perhaps because the FW & ethernet controllers in the iMac G5 are the same PHY chip? Is this some kind of contention for bandwidth through the PHY chip? (The Airport card in the iMacG5 is on a separate bus, not connected to the Ethernet/FW PHY chip, which makes me suspect something is up with the ethernet/FW controller.)
Anyone else encounter a problem like this with slow file transfer through your iMacG5 to an external FW drive?

Answer 1

Martin, that's really interesting. I've noticed slow network transfers in the past but always racked it up to overhead and parity errors inherent in the OS's. Never thought it might be the PHY chip, though it certainly could be. Apple has a broadband tuner which might help you by increasing packet size (but you probably knew that as a Level3). My stopgap is to do the file transfers with firewire, but your laptop may not have that option.
You could maybe copy to the mac over the network, then copy a second time to the LaCie. Not elegant or clean, but will save you time. Kinda like taking the backroads to avoid rush hour traffic - it's farther to go but you get there faster.
I'll look into the controller question. Let us know how you're doing,
Ed