ethernet slow on LAN

[JHSJ]

I have a problem I don't know how to solve and it's a deal-breaker for me=
=2E

Synopsis of the problem:  I can only get about 70kBs transfer rate when f=
tping=20
files between 2 machines on the LAN in my home.

Equipment:

Two machines:=20

1.  A laptop:  Powerbook G3 Series 266mhz, 192MB RAM, built-in ethernet,=20
YellowDog 2.3 unmodified;  static IP via dsl

2. An early 2001 iMac running OS X, connected to the LAN via built-in=20
ethernet.

The setup:

My DSL modem is connected to the uplink on my Linksys 5 port Workgroup Hu=
b.
The 2 computers are connected to the Linksys Hub.  Each computer has a st=
atic=20
IP provided by the DSL provider. =20

When I run OS X or MacOS 9 on both machines, I don't have this problem.  =
But=20
as soon as I run Linux on the laptop (or the iMac) then my transfer speed=
s=20
drop from a full 1MB/s to 70 kBs. =20

I have aboput 40G of files that I need to transfer from the laptop to the=
=20
iMac.  70kBs is way too slow.  Any ideas where to start looking?
"Try ifconfig" you say?  Ok:

eth0      Link encap;Ethernet  HWaddr 00;05;02;7C;FD;FB            inet=20
addr;66.92.133.95  Bcast;66.92.133.255  Mask;255.255.255.0          UP=20
BROADCAST RUNNING MULTICAST  MTU;1500  Metric;1          RX packets;77403=
98=20
errors;118 dropped;0 overruns;0 frame;0          TX packets;3944113 error=
s;1=20
dropped;0 overruns;0 carrier;0          collisions;0           RX=20
bytes;3023883986 92883.8 Mb0  TX bytes;371848739 9354.6 Mb0lo        Link=
=20
encap;Local Loopback            inet addr;127.0.0.1  Mask;255.0.0.0      =
   =20
UP LOOPBACK RUNNING  MTU;16436  Metric;1          RX packets;28 errors;0=20
dropped;0 overruns;0 frame;0          TX packets;28 errors;0 dropped;0=20
overruns;0 carrier;0          collisions;0           RX bytes;1740 91.6 K=
b0 =20
TX bytes;1740 91.6 Kb0

But what does that mean?
FWIW, the main difference that I see between ifconfig on OS X and on Linu=
x is=20
that on OS X, it says (for en0):
SIMPLEX=20
and it does not say that on the Linux box.  And that makes me think the O=
S X=20
box is running (properly I guess) in half-duplex and the Linux box is try=
ing=20
to run in full Duplex?   If that's the case, how do I fix it?

Another bit of info:
When I upload via ftp FROM the laptop (running YDL 2.3) TO the OS X iMac,=
 I=20
get 70kBs.  But when I upload FROm the OS X imac TO the laptop YDL 2.3, I=
 get=20
800kBs.

Can someone please tell me how to fix this?

Thank you!

Jeff