From owner-freebsd-arch  Mon Dec 17 18:48:51 2001
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To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Subject: Re: Please review: changes to MI bus code for sparc64 
Cc: arch@FreeBSD.org
In-reply-to: Your message of "Mon, 17 Dec 2001 21:36:17 EST."
		<200112180236.fBI2aHM39997@khavrinen.lcs.mit.edu> 
References: <200112180236.fBI2aHM39997@khavrinen.lcs.mit.edu>  <20011213211544.A4747@crow.dom2ip.de> <20011213192033.A871@crow.dom2ip.de> <200112131901.fBDJ1hl02003@mass.dis.org> <20011213211544.A4747@crow.dom2ip.de> 
Date: Mon, 17 Dec 2001 19:48:45 -0700
From: Warner Losh <imp@harmony.village.org>
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In message <200112180236.fBI2aHM39997@khavrinen.lcs.mit.edu> Garrett Wollman writes:
: In article <200112180212.fBI2CUM81074@harmony.village.org> you write:
: >I don't understand the difference between boundary and alignment.
: 
: A boundary is a locus which an allocation must not cross.  Consider,
: for example, the crufty old ISA DMA hardware: 16-bit transfers need
: only 16-bit alignment, but must not cross a 64-kbyte ``page''
: boundary, because the address-generation logic was kluged out of a
: 16-bit DMA controller and an 8-bit latch.

Ah.  That makes perfect sense.  It doesn't need 64kbyte alignment, but 
must not cross a 64kbyte boundary...

Warner

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