Yet Another TSE/SGDMA/Simple Socket Server Post

It's not a hardware problem, it's a software problem. If you are using the Interniche TCP/IP stack there is a special include file (I think it's called ipport.h) where you can redefine macros to allocate/deallocate memory for packets. Some example designs show how to use on chip memory to speed up the TCP/IP stack, so if you started with one of such examples it will try and write the packet contents to that memory. If you remove those macros it should use the main heap memory instead. You'll find information about that in [url=https://altera.com/content/dam/altera-www/global/en_US/pdfs/literature/an/an440.pdf]application note 440, pages 9 and over (Using Faster Packet Memory).