AST RESEARCH, INC.       INFORMATIONAL BULLETIN # 0031       02/25/97 
 
 
 
TITLE:  DIMM Substitution in AST Systems
 
 
SUMMARY 
 
   When attempting to use Dual In-line Memory Modules (DIMMs) from 
   different systems keep in mind that all DIMMs are not necessarily 
   interchangeable. 
   
   Not all DIMMs are designed to the same technical specifications. 
   DIMMs can require different operating voltages, use different 
   memory architectures, contain a different number of pins, or 
   include a number of other differences. 
   
   Some DIMMs are keyed in two places, while others are keyed in 
   three places, to prevent the user from installing DIMMs into the 
   incorrect sockets. When viewed from the front, the leftmost key 
   position indicates the type of Dynamic Random Access Memory 
   (DRAM) module used (buffered, unbuffered, etc.) while the center 
   key position denotes supply voltage (3.3V or 5V).
   
   This issue applies to all Manhattan S and Manhattan D systems.    
 
 
NOTES 
 
   At the time this document was written, there were two families of 
   AST server systems which use DIMMs: the Manhattan S series and 
   the Manhattan D series and their derivatives.
   
   The Manhattan S series uses a 5V, 168 pin DIMM such as AST part 
   number 104000-228 which is an IBM IBM11M4730CF (or equiv.) 4M x 
   72 (ECC-optimized).  The corresponding part for a Manhattan D is 
   a 3.3V, 168 pin DIMM, such as AST part number 104210-049 which is 
   a Samsung KMM372F400BK-6 (or equiv.) 4M x 72 ECC/EDO.
   
   The above manufacturers' part numbers are used for illustrative 
   purposes only. AST qualifies components from a number of 
   different vendors so the components in your system could be 
   different than those used in the above examples.
   
   If you are attempting to verify third-party DIMM compatibility in 
   your system, refer to the appropriate manufacturer's data sheet 
   for the particular DIMM in question.  AST does not guarantee 
   proper system operation, if unqualified memory is used.    
 
 
TAN N/A 
 
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