AST RESEARCH TECHNICAL BULLETIN TB-0177                    6-4-86


        REX.SYS MEMORY ALLOCATION AND IBM XT MODEL 516089


While  testing was being conducted on the Model 516089 (new)  IBM 
PC-XT, a possible discrepancy was observed with REX.SYS (Extended 
Memory   Emulator).    Two   identical   XT's   with   the   same 
configurations   were   used.    Both  XT's  had   subdirectories 
containing the REMM.SYS and REX.SYS files.   Both XT's  contained 
CONFIG.SYS  files with the proper paths specified to REMM.SYS and 
REX.SYS.

One  XT  worked properly and allocated the  specified  amount  of 
memory to REX.SYS.  

The second XT is where the discrepancy was noticed.  When REX.SYS 
is invoked from a subdirectory,  regardless of how much memory is 
allocated  to REX.SYS,  it will only accept 64K bytes of extended 
memory emulation (REX).   However,  when REX.SYS is invoked  from 
the  root directory,  the amount of memory allocated is equal  to 
the amount specified.

If  this problem is encountered,  it is suggested to put REMM.SYS 
and REX.SYS in the root directory.