AST RESEARCH TECHNICAL BULLETIN TB-0003A                  4-30-84


                MEMORY SWITCH ERROR IN IBM GUIDE 
                TO OPERATIONS FOR IBM PORTABLE PC


When  extending the memory size of the IBM Portable PC beyond the 
128K minimum capacity of the system motherboard, the procedure is 
essentially the same as that for the XT.

Additional  memory may be installed on the I/O bus without  first 
fully populating the motherboard.   However,  it is necessary  to 
indicate  the amount of motherboard memory installed via switches 
3 and 4 of the system motherboard switch block.

Unfortunately,  page  4-81 of the IBM Guide to Operations  Manual 
erroneously  shows  that  the  switch position for  256K  on  the 
motherboard  is switch 3 off and switch 4 on.   This is  actually 
the setting for 128K of RAM.

The following is the proper settings for switches 3 and 4 of  the 
system motherboard switch block.

          AMOUNT OF MEMORY             SWITCH        SWITCH
      INSTALLED ON MOTHERBOARD            3             4

                128K                     OFF           ON

                192K                     ON            OFF

                256K (fully populated)   OFF           OFF