this seems like a wan/lan network issue ... if there is a way you can get both boxes on the same subnet, you might get the transmit speed to go much higher ...
if both boxes are already on the same subnet, check the settings on the network switch ports themselves to make sure they are not on auto ...
if the NICs and ports for both boxes are already set correctly and there are no issues with any of the network devices connecting the SCO box to the Linux box, try a "temporary enhancement" if possible ...
Code:
1. power-off both boxes
2. remove older box's smaller drive and add it to an empty slot on the newer box
3. boot up newer box
4. if newer box can read data on "new" drive, copy data
5. power-off new box
6. remove "new" drive and return to older box
7. boot up both boxes normally
