Old design R2000 and Realtek RTL8019AS duplex issue

 
 I have an OLD design based on the TCP/IP demo board.  It used the R2000 and the Realtek8019AS Ethernet chip.
  
 I am using the DC8.61 compiler.
  
 For YEARS customers have been running this without issue.  Now one customer is demanding we switch to Full Duplex.
  
 I put the #define RT_FULLDUPLEX in the code but it has not switched to full duplex.  We are monitoring the state by connecting thru a switch the indicated whether we are half or full duplex.
  
 By comparing the binaries, I can see that the code has changed to make use of the new define, but nothing seems to have changed on the port.
  
 Can anyone comment on this?
  
 -Pete F