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From: bruceb@amiga.UUCP (Bruce Barrett)
Newsgroups: net.micro.amiga
Subject: Re: Speed of seeks
Message-ID: <1121@amiga.amiga.UUCP>
Date: Wed, 7-May-86 13:22:29 EDT
Article-I.D.: amiga.1121
Posted: Wed May  7 13:22:29 1986
Date-Received: Sat, 10-May-86 13:33:33 EDT
References: <12593@ucla-cs.ARPA>
Reply-To: bruceb@hunter.UUCP (Bruce Barrett)
Distribution: net
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 31

In article <12593@ucla-cs.ARPA> cc1@ucla-cs.UUCP (Michael Gersten) writes:
>Wait a sec... A Seek() call on the Amiga HAS to read every sector.
>
>Each sector on the amiga contains a (byte, word, long, whatever) indicating
>how much of the sector is used. 
	True.  It's a long.  For floppoies it's >0 and <=488
>So, if you want to read byte 600, you can't
>just go to the second record-- you have to go to the first, find out how
>much space it uses, go to the second, find out how much, etc.
	False.  One sector is filled before the next is started.
>
>Incidently, Amiga, how is your disk arrainged? Is it 80 tracks, 160 tracks,
>single sides, double sided, 512 bytes, 256 words, 128 long words, etc.
For 3.5" Floppy:
	2	surfaces
	40	cylinders
	11	blocks per track
	512	bytes per block.
	488	usable data bytes per sector.

The 24 byte difference (512-488) is 6 long words (4 bytes each):
	sector type = data
	header key
	sequence numver
	data size (thus the confusion)
	next data block number (forward link)
	checksum for the sector

Hope that helps!
--Bruce Barrett
--C-A