Path: utzoo!attcan!uunet!mcsun!hp4nl!sci.kun.nl!cs.kun.nl!lwj
From: lwj@cs.kun.nl (Luc Rooijakkers)
Newsgroups: comp.os.minix
Subject: Re: Disk address size in V2.0
Message-ID: <2287@wn1.sci.kun.nl>
Date: 12 Oct 90 14:24:28 GMT
References: <32993@nigel.ee.udel.edu>
Sender: root@sci.kun.nl
Lines: 38

burgess%creek.decnet@hsdp2.brooks.af.mil (CREEK::BURGESS) writes:

>  I have always been a firm believer in internal consistency.  If you are going
>to use 4-byte address in memory, why obfuscate the method and waste the time 
>converting them back and forth reading them from disk?

The disk addresses have to be converted anyway from/to "standard" byte
order on disk, to keep the various computers compatible. With 4 byte
addresses you might use BSD's ntohl()/htonl() functions, but the
conversion has to be done anyway. What's the difference between

	unsigned long blk;
	unsigned char *ptr;

	blk =*ptr++; blk<<=8;
	blk|=*ptr++; blk<<=8;
	blk|=*ptr++;
	
and

	unsigned long blk;
	unsigned char *ptr;

	blk =*ptr++; blk<<=8;
	blk|=*ptr++; blk<<=8;
	blk|=*ptr++; blk<<=8;
	blk|=*ptr++;

except for a few cycles ? Similar code exists in V7 (I know, I've seen
it). I would say that the decision has to be made solely on "small
files" versus "maximal disk capacity". Why repeat the 16-bit cluster
number mistake of MS-DOS with 24 bits ? Of course, we're talking about
zones, and with 1K zones 2^24 is already 16G...

--
Luc Rooijakkers                                 Internet: lwj@cs.kun.nl
Faculty of Mathematics and Computer Science     UUCP: uunet!cs.kun.nl!lwj
University of Nijmegen, the Netherlands         tel. +3180652271