<PAGE>
 
                                  EXHIBIT 11

                       INTEGRATED CIRCUIT SYSTEMS, INC.

                        COMPUTATION OF PER SHARE INCOME
            ($ and shares in thousands, except for per share data)

<TABLE>
<CAPTION>
                                                               Three months ended             Six months ended             
                                                             ----------------------         -------------------           
                                                               Dec. 28,   Dec. 30,           Dec. 28,  Dec. 30,                
                                                                 1996       1995               1996      1995                  
                                                             ----------   ---------        ----------  --------           
<S>                                                          <C>          <C>              <C>         <C>                     
Primary                                                                                                                        
-------                                                                                                                        
Net income                                                   $    2,246   $   1,894         $   2,875  $  6,055                
                                                             ==========   =========         =========  ======== 
Common and common equivalent shares outstanding:                                                                                
   Weighted average common shares outstanding                    11,211      11,286            11,265    11,233                 
   Assumed exercise of stock options                                168         395                81       581                 
                                                             ----------   ---------         ---------  --------     
                                                                 11,379      11,682            11,346    11,814                 
                                                             ==========   =========         =========  ========     
Earnings per common share and common equivalent shares       $      .20   $     .16         $     .25  $    .51        
                                                             ==========   =========         =========  ========                 
                                                                                                                   
Fully Diluted                                                                                                                   
-------------                                                                                                      
Net income                                                   $    2,246   $   1,894         $  2,875   $  6,055         
                                                             ==========   =========         ========   ========                 
                                                                                                                   
Common and common equivalent shares outstanding:                                                                                
   Weighted average common shares outstanding                    11,211      11,286           11,265     11,233                 
   Assumed exercise of stock options                                277         401              280        590                 
                                                             ----------   ---------         --------   --------     
                                                                 11,488      11,687           11,545     11,823                 
                                                             ==========   =========         ========   ========     
Earnings per common share and common equivalent shares       $      .20   $     .16         $    .25   $    .51     
                                                             ==========   =========         ========   ========     
</TABLE>

19