"Cannot disable A20 line" warning msg from HIMEM.SYS

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#4244

From: Agent of Goldstein
Date: Mon, 29 Oct 1990 05:45

24 lines
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When my system, a 386sx with NEAT motherboard, boots up I get the following
message from HIMEM.SYS:

	Installed A20 handler number 1.
	WARNING: Can't disable A20
	64K High Memory Area is available.

This occurs even if HIMEM is the only thing in the CONFIG.SYS file,
so it should not be a conflict with another memory manager.

I'm new to Intel/IBM architecture and don't really understand what
this message means or what its implications are; other than that
the A20 line has to do with an address line used in memory management.  

The system appears to otherwise function normally.  I know I have *not* 
seen this WARNING message on other systems as they boot up.  Any 
insights/explanations appreciated! 

-------------------------------------------------------------------------------
  Bob Alpert       { alpert@chovax.dec.com            }  Suspicion breeds
  DEC              { ...!decwrl!chovax.dec.com!alpert }  confidence.
  Cherry Hill, NJ  { alpert%chovax.dec@decwrl.dec.com }  
-------------------------------------------------------------------------------

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From: alpert@chovax.enet.dec.com (Agent of Goldstein)
Newsgroups: comp.sys.ibm.pc.misc,comp.sys.ibm.pc.hardware
Subject: "Cannot disable A20 line" warning msg from HIMEM.SYS
Keywords: a20 himem memory management
Message-ID: <16772@shlump.nac.dec.com>
Date: 29 Oct 90 05:45:21 GMT
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Organization: Digital Equipment Corporation
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