Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!elroy!gryphon!jdow
From: jdow@gryphon.CTS.COM (J. Dow)
Newsgroups: comp.sys.amiga
Subject: Re: Request to Commodore (Fast File System)
Message-ID: <6177@gryphon.CTS.COM>
Date: 2 Sep 88 07:45:00 GMT
References: <8808291950.AA12753@cory.Berkeley.EDU> <4604@cbmvax.UUCP>
Reply-To: jdow@gryphon.CTS.COM (J. Dow)
Organization: Wizardess Designs, Hermosa Beach, Ca
Lines: 57

In article <4604@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes:
>in article <8808291950.AA12753@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) says:
>> 
>> :  I was thinking a while back about the Fast File System not being put on the
>> :  floppies  in AmigaDos 1.3.  It is  my  understanding  ...
>> 
>> 	What I would like to see is an unmount command.... to unmount a 
>> device (i.e. DF0:) then remount it under the new filesystem.  Even better,
>> have the OS detect the disk format (easily done) and use the proper filesystem.
>
>You mean like 1.3's "Assign UNMOUNT DF0:" 
>
>> 							-Matt
>
>You could probably set up a floppy with FFS, and it would be fast.  The other
>problem you'd have is that it wouldn't know when a block went bad.  The standard
>file system stores a 32 bit checksum in the block header of each block on your
>disk.  Under FFS, there is no block header for data blocks.  This has the nice
>feature of letting you store 512 bytes per block instead of 488, and it also
>lets multiple blocks be transferred directly to their destination, without
>any stripping.  This makes lots of sense using hard disks or similar devices 
>that do hardware error checking that's far superior to the file system's 
>checksum.  However, with a floppy, there is no underlying hardware error
>checking logic; the checksum is all you get. 
>-- 
>Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
>   {ihnp4|uunet|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
>		"I can't relax, 'cause I'm a Boinger!"

Er say what? I have page 49 of the DevConII notes for the hardware section open
in front of me. Acto it there is the following sector organization:
2 bytes of 00 data - MFM = AAAA each
2 bytes of A1* - standard sync byte encoded A1 without clock pulse
1 byte format byte - amiga 1.0, 1.1, 1.2 == FF
1 byte track number
1 byte sector number
16 bytes of OS recovery info per note 2 (left out here)
four bytes header checksum
four bytes of data area checksum
512 bytes of data

And this all repeats for each sector. So the floppies DO TOO have a checksum
safety in them besides the SECOND checksum embedded within oldfs.

Or do these C= notes lie to me?
{O_O}

-- 
Sometimes a bird in the hand leaves a sticky deposit.
Perhaps it were best it remain there in the bush with the other one.

{@_@}
	jdow@bix (where else?)		Sometimes the dragon wins. Sometimes
	jdow@gryphon.CTS.COM		the knight. Does the fair maiden ever
	{backbone}!gryphon!jdow		win? Surely both the knight and dragon
					stink. Maybe the maiden should suicide?
					Better yet - she should get an Amiga and					quit playing with dragons and knights.