AST RESEARCH TECHNICAL BULLETIN TB-0143                   1-15-86


                   TWO SIXPAKPLUS CLOCK CHIPS


Recently,  the clock chip on the SixPakPlus has been changed to a 
different vendor.   The latest version of the SixPakPlus utilizes 
a  Ricoh  RP5C15,  as  opposed  to the earlier  versions  of  the 
SixPakPlus  using a National Semiconductor part  number  MM58167.  
Since  this change has taken place,  the question has been raised 
as  to  how  the ASTCLOCK.COM program   (included  with  SuperPak 
Version 4.3) can tell the difference between these two chips.

Internal address "D" is used by ASTCLOCK to determine which  chip 
is being used.  The address was chosen for the following reasons.  
For the Ricoh clock chip,  this address is a "read-only" address; 
it  ALWAYS  returns a "0" when read.   The same address  for  the 
National Semicoductor chip is RAM  and will read back whatever is 
written to it.

So ASTCLOCK writes a "1" to address D, bit one.  If the result is 
a "0",  the program knows a Ricoh chip is present and goes to the 
appropriate place within the program to read this chip.  

Conversely,  if a "1" is read back by ASTCLCOK,  then the program 
knows  to use the portion of the clock dedicated to the  National 
Semiconductor chip.