Path: utzoo!mnetor!uunet!husc6!think!ames!amdahl!oliveb!sun!pepper!cmcmanis
From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: comp.sys.amiga
Subject: Re: Is AmigaDOS sane?
Message-ID: <39427@sun.uucp>
Date: 20 Jan 88 19:14:05 GMT
References: <30217R38@PSUVM>
Sender: news@sun.uucp
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 30

In article <30217R38@PSUVM> R38@PSUVM.BITNET (aka Marc Rifkin) writes:
> First of all, a newly formatted disk does not have even close to '880k',
> I know there is usually some overhead used by the DOS, but HOW MUCH?
> Also, I have noticed some inconsistencies in block allocation- such as
> putting say 600k on a disk and then checking to find close to 100k free.
> What is going on here?

The maximum data storage on a floppy disk is 80 Cylinders * 22 sectors/Cyl
* 488 bytes/sector or 838K, however DOS reserves two blocks for booting,
1 block for the root block, and one block for the bitmap page. Thats
4 blocks or 1.9K (Note K = 1024), now a file needs at least one block
for the file header and one block for every 'extension' I believe you 
get 72 pointers/file header so every 73 blocks, one is needed to hold
the pointers Since we have 1756 blocks left divide that by 73 gets us
24 and some change, or 25 blocks to hold the file header and pointers.
So the biggest file you could hope to put on a floppy would be 
1760 - 4 - 25 = 1731 blocks or 824.9K bytes.

Note that 'info' lies to you about how much space is available on the
disk because it multiplies free blocks by '512' rather than the value
in BYTESPERBLOCK. My version of the Info command let you see the 'real'
sizes. 
     
>PS:  68040 is in development, and it sounds like a BEAUTY!!

And I here the 80586 has a virtual Cray X-MP mode! :-)

--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.