Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!henry From: henry@utzoo.UUCP (Henry Spencer) Newsgroups: comp.unix.wizards Subject: Re: BSD 4.2 minphys() < 64K Message-ID: <7423@utzoo.UUCP> Date: Tue, 16-Dec-86 17:41:53 EST Article-I.D.: utzoo.7423 Posted: Tue Dec 16 17:41:53 1986 Date-Received: Tue, 16-Dec-86 17:41:53 EST References: <376@wyszecki.munsell.UUCP> Organization: U of Toronto Zoology Lines: 17 > Why does minphys() in BSD 4.2 systems still limit block i/o transfers to > 63 * 1024 bytes? I assume that this is an ancient artifact from PDP-11 > days... Provided the disk controller and the bus being used can cope, I can't see any good reason to retain the restriction. Bear in mind that most Unibus controllers tend to use 16-bit transfer-size counts, and any Unibus I/O is limited by the 256KB Unibus hardware address space. For non-Unibus controllers, I can't see any good reason for the limitation unless there is some other stupid problem with the VAX hardware (I don't have a VAX and don't want one). This doesn't mean that there isn't something silly in Berklix that will break if you remove the limit... -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,decvax,pyramid}!utzoo!henry