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+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
+