GM knock sensing

[dzorde at aesprodata.com.au]

     On the business of knock sensing (especially GM).  Does anyone know 
     how the 5 pin ignition module works.  I figured it is similar to a 4 
     pin module, but somehow the 5th pin from the est module is used to 
     retard the timing.  How is this done in the ignition module ?
     
     Also I want to connect the old style HEI dizzy to the computer for 
     computer controlled mapping.  Can the 7 pin module be fitted in this 
     dizzy ? and does it have the reguired output (tacho signal) to the 
     computer as well as the required input (coil drive signal) from the 
     computer ?  I read something about a 5V bypass signal on the 7 pin 
     module, what's this for ?
     
     Hopefully thanks in advance
     
     Dan        dzorde at aesprodata.com.au