Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site decwrl.UUCP Path: utzoo!linus!vaxine!wjh12!genrad!decvax!decwrl!dec-rhea!dec-dosadi!binder From: binder@dosadi.DEC (The Stainless Steel Rat) Newsgroups: net.micro.apple Subject: Re: Apple disk speed -- more info Message-ID: <1483@decwrl.UUCP> Date: Thu, 14-Jun-84 08:58:50 EDT Article-I.D.: decwrl.1483 Posted: Thu Jun 14 08:58:50 1984 Date-Received: Wed, 20-Jun-84 00:33:02 EDT Organization: DEC Engineering Network Lines: 43 I don't know how the Mac does it, but the Apple ][ DOS places data on the disk sequentially backward, thus: Imagine a 16-sector file, ie one track, to be saved on a freshly initialised disk. This file will be stored in this order on the disk: File sector Disk track/sector File sector Disk track/sector ----------- ----------------- ----------- ----------------- 1 18/15 9 18/ 7 2 18/14 10 18/ 6 3 18/13 11 18/ 5 4 18/12 12 18/ 4 5 18/11 13 18/ 3 6 18/10 14 18/ 2 7 18/ 9 15 18/ 1 8 18/ 8 16 18/ 0 ...and so on for longer files. What this means in terms of read/write time is that a simple-minded DOS can have lots of time to read a sector into a buffer area and then move it to the proper area in memory, and then do housekeeping before the next sector comes along, almost a full revolution later. Thus, it takes DOS 3.3 18 revolutions to read that 16-sector file. SLOOOOOOOWWW!!! There are several third-party DOSes available for the Apple ][ machines; three that I know of are Diversi-DOS, from DSR, Inc.; ProntoDOS, from Beagle Brothers; and David DOS, from David Data. All of these are smarter in that they don't need the massive amount of time between sectors. They use a little intelligence to read sectors out of order, and all of them can load a 16-sector Applesoft or binary programme in only TWO revolutions. Text file handling is a little slower but still vastly faster than DOS 3.3. All of these DOSes also include extra functions, some of them rather nice; David DOS has new commands for direct load and save of text files, Diversi-DOS has a TLIST command that lists Applesoft directly from the disk, and so on. Cheers, Dick Binder (The Stainless Steel Rat) UUCP: { decvax, allegra, ucbvax }!decwrl!rhea!dosadi!binder ARPA: binder%dosadi.DEC@decwrl.ARPA Posted Thursday 14th June 1984, 08:59 Eastern time by DOSADI::BINDER