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From: ron@topaz.rutgers.edu (Ron Natalie)
Newsgroups: comp.unix.wizards,comp.unix.questions
Subject: Re: Another Annoying Microport Inquiry
Message-ID: <15478@topaz.rutgers.edu>
Date: Sat, 10-Oct-87 18:19:23 EDT
Article-I.D.: topaz.15478
Posted: Sat Oct 10 18:19:23 1987
Date-Received: Mon, 12-Oct-87 18:46:11 EDT
References: <1408@dasys1.UUCP> <6475@brl-smoke.ARPA> <116@suprt.UUCP> <4419@teddy.UUCP> <30555@sun.uucp>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 17
Keywords: Microport patch ulimit
Xref: mnetor comp.unix.wizards:4820 comp.unix.questions:4486

>  Maybe the people for whom the predecessor of System V was
> designed were running PWB/UNIX shops - PWB/UNIX 1.0 had a modified V6 file
> system, with no doubly-indirect blocks, which meant they had an absolute
> file size limit of 1MB - and they didn't want these people to have to learn
> something new, such as how to deal with files larger than 1MB....

You're memory is failing you.  V6 file systems have doubly indirect blocks.
You either have eight direct blocks (LARGE bit in mode word = 0), or seven
single-indircect (Large bit on), or a huge file.  The block number in the
inode is used as a double indirect block.  The main limitation is that the
file size in the inode was 24 bits.  (An amuzing V6 bug is that the file
offsets were 32 bits, so you could seek to 2^24-1 and write a char and your
file would appear to be zero length).

Another V6 limitation is that early file systems could not be more than 32,767
blocks long.  Careful bug fixing can increase this to full 16 bit block number
size.  PWB 2.0 used V7 filesystems (I believe, I never saw it).