From: uhclemLOSE.aug08@nemesis.lonestar.org   
      
   Joe Zwerko  wrote:   
   : I've managed to lay hands on a WD2143, but the package marking is   
   : "WD2143PD", and the next line has "03-15", then the date code.  (First line   
   : says (C)WDC '81) The 1982 Tandy repair manual specifies a WD2143-01, and   
   : Knut's photo shows a WD2143M-03.  The only data sheet I've seen is for   
   : WD2143-03... no M, no PD.  Does anyone know what the M and PD specify?  The   
   : data sheet gives no detail on the package markings at all.   
      
      
   According to Page 527 (Ordering Information) of the 1984 Storage   
   Management Products book from Western Digital, "M" is an obsolete   
   package designator meaning "18 Lead DIP-Plastic (Totally Encapsulated),   
   while "PD" is the newer code for Plastic Encapsulated with 18 leads.   
   So this is another way to say the same thing, and it likely doesn't   
   affect your ability to use the part.  Having a "M" vs a "PD" simply   
   means the "M" part was made before this change in markings.   
      
      
   For future reference, here are the Western Digital Package Designations   
   from that period.   
      
   WESTERN DIGITAL OBSOLETE [AS OF JUNE 1984] PACKAGE DESIGNATIONS   
   A	40 Lead DIP-Ceramic   
   B	40 Lead DIP-Relpak   
   C	24 Lead DIP-Ceramic   
   E	28 Lead DIP-Ceramic   
   F	28 Lead DIP-Relpak   
   M	18 Lead DIP-Plastic (Totally Encapsulated)   
   P	40 Lead DIP-Plastic (Totally Encapsulated)   
   R	28 Lead DIP-Plastic (Totally Encapsulated)   
   T	48 Lead DIP-Ceramic   
   U	20 Lead DIP-Ceramic   
   V	20 Lead DIP-Plastic (Totally Encapsulated)   
   X	Ceramic Kit   
   Y	Plastic Kit   
      
   Example of obsolete [as of June 1984] method:   
   WD1943M00 Where M = Single Digit   
   Package Designator (M = Lead Plastic)   
      
      
   WESTERN DIGITAL CURRENT [AS OF JUNE 1984] PACKAGE DESIGNATIONS   
   [This is a two-character code]   
      
   PACKAGE TYPE:				LEAD COUNT:   
   A	Ceramic Side Braze		A	<14 Lead   
   C	Cerdip				B	14 Lead   
   P	Plastic (Encap)			C	16 Lead   
   D	Ceramic Chip			D	18 Lead   
   	Carrier-Leadless		E	20 Lead   
   G	Ceramic Chip			F	22 Lead   
   	Carrier-Leaded			G	24 Lead   
   H	Plastic Chip			H	28 Lead   
   	Carrier-Leadless		L	40 Lead   
   J	Plastic Chip			M	44 Lead   
   	Carrier-Leaded			N	48 Lead   
   					S	64 Lead   
   					T	68 Lead   
   					X	Kit   
      
   Example of current [as of June 1984] method:   
   WD1943PD00 Where PD = Double Digit   
   Package Designator (P = Plastic and D = 18 Lead)   
      
   [The manual does not state when this code change occurred.]   
      
      
      
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