The IBM 16/4 Busmaster Adapter /A is a 24 bit DMA adapter. As such it attempts to directly access memory. Since it is only a 24 Bit adapter, it CANNOT address memory above the 16 Mb line. If the advanced server has defined a cache above the 16 Mb line, the Busmaster adapter /A cannot read that information. Thus you will see a number of server failures including hangs.
This problem is not present with non-busmaster 16/4 Adapter /A's. The reason is that these adapters are shared RAM adapters and thus do not access memory directly. The Operating System takes care of making all calls to memory.
In many cases within the server, data is transferred directly from the file system cache to the network. If the network adapter cannot address above 16M, then the cache cannot be placed above 16M, since it may have to be transferred out of it. This is generally up to the network card device driver to control, however the USEALLMEM parameter switch may be used to tell 386 HPFS whether or not to use above 16 MB.
To have LAN Server v2.0 Advanced or LAN Server v3.0 Advanced use ONLY the memory below the 16 you need to remove the USEALLMEM parameter from the HPFS386.IFS line. This parameter instructs LAN Server to use all memory in the system when defining Cache. Without the USEALLMEM parameter, LAN Server will use only the memory below the 16 Mb line. Remove this parameter ONLY on systems with greater than 16 Mb RAM AND an IBM 16/4 Busmaster Adapter /A.
The consequence of removing USEALLMEM is that the file cache can't exploit all of your installed memory. If you want a file cache larger than about 8 megabytes you will need to use a standard 16/4 adapter (non-busmaster) or you will need a 32-bit busmaster adapter.