Path: utzoo!attcan!uunet!husc6!mailrus!ames!amdahl!amdcad!diablo!phil
From: phil@diablo.amd.com (Phil Ngai)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Usable I/O Address range on the PC bus ...
Keywords: Limited to addresses up to 0x0400 only??
Message-ID: <23607@amdcad.AMD.COM>
Date: 22 Nov 88 00:56:25 GMT
References: <5065@whuts.ATT.COM> <4229@encore.UUCP> <1275@cfa.cfa.harvard.EDU>
Sender: news@amdcad.AMD.COM
Reply-To: phil@diablo.AMD.COM (Phil Ngai)
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
Lines: 15

In article <1275@cfa.cfa.harvard.EDU> ward@cfa.harvard.EDU (Steve Ward) writes:
|  Just to prevent misunderstanding, there are 64 images, or "copies"
|  of each of the 1024 I/O byte-addressable registers, or I/O byte
|  locations.  This means any I/O addressing done to any of these
|  64 "imaged, copied, ghosted, etc" address locations will result
|  in an access to the same I/O byte location.

This is true of the motherboard and many plug-in cards you can buy.
You are not bound by this restriction if you design your own hardware.
Also, LIM EMS memory boards are a notable exception to this rule as well. 

--

Phil Ngai, phil@diablo.amd.com
{uunet,decwrl,ucbvax}!amdcad!phil