XPost: comp.os.ms-windows.misc, alt.windows7.general, microsoft.   
   ublic.windowsxp.general   
   From: TimSlattery@utexas.edu   
      
   Steve Hayes  wrote:   
      
      
   >I think early programs running on IBM PC DOS or MS DOS were 8-bit,   
   >running on 8088 processors. The 286 and 386 ones were 16-bit.   
      
   Not so. The original IBM-PCs were 16-bit machines. They used a kludge   
   to implement a 20-bit address space, allowing access to one megabyte   
   of RAM. You may remember that 340KB of that was reserved for the   
   operating system, leaving 640KB for user program.   
      
   1970's vintage machines, such as Cromemco, Zylog, etc, etc, were 8   
   bits. I'm a bit foggy on their addressing schemes, but at least some   
   of them could switch between banks of 64KB each.   
      
   The 80286 was basically 16-bits, but implemented "protected mode"   
   which allowed access to 16MB. Windows programers (if they're old   
   enough) may remember using "GlobalAlloc" and "GlobalFree" calls. Those   
   manipulated the Global Allocation Table, a 80286 protected mode   
   hardware kludge that kept track of all that RAM.   
      
   The 80386 was Intel's first true 32-bit machine. Windows 3.0 386   
   version ran in 16-bit 80286 protected mode though. It took a while for   
   Windows to catch up with 32-bit processors.   
      
   --   
   Tim Slattery   
   timslattery  utexas  edu   
      
   --- SoupGate-Win32 v1.05   
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