Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!sri-spam!sri-unix!hplabs!decwrl!decvax!tektronix!uw-beaver!cornell!batcomputer!braner
From: braner@batcomputer.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Disk speeds on Atari ST and Macintosh
Message-ID: <2165@batcomputer.tn.cornell.edu>
Date: Sat, 31-Jan-87 00:57:42 EST
Article-I.D.: batcompu.2165
Posted: Sat Jan 31 00:57:42 1987
Date-Received: Sun, 1-Feb-87 12:19:13 EST
References: <8701290450.AA16048@cory.Berkeley.EDU>
Reply-To: braner@batcomputer.UUCP (braner)
Organization: Theory Center, Cornell University, Ithaca NY
Lines: 31
Summary: The theoretical speed is seldom achieved

[]

In BYTE benchmarks the Mac+ is FASTER in floppy speed than the ST.
(Note that '+').  The speed of reading long files on the ST by the system,
in the case where it simply dumps the data in RAM (e.g. loading a long
program), is about one-half of the theoretical speed of 5 tracks per second
(due to 300 rpm, which is 22.5 Kbytes/sec with 4.5K per track).
Reading text files by programs that call the system for each character
is a LOT slower, and writing is also slower due to the read-after-write
verification.  Some sophisticated programs (e.g. STCOPY 2.0) DO read the
disk right at the theoretical limit.

As for hard disks, in practice the speed is limited by track-to-track
head movement speed and the system's approach to reading system info
(e.g. directory and FAT sectors).  TOS does not cache those, and ends
up moving the head a LOT.  I'm not sure what the Mac does, but I have
read a review of several hard disks for the Mac in a Mac mag, and the
conclusion was that in normal use all the hard disks had about the same
speed (hinting of software (OS) limit on speed) and that that speed was
only about twice the speed of floppies (I can't remember if it was the
old (toy) Mac or the Mac+ (a real computer)).  The mention of "HD reading
at the theoretical maximum speed" must refer to some specialized software.
(I am NOT trying to rekindle the "my computer is better" war.  Leave the
religious wars to the Ayatollas, please!)

The speed of the DMA port on the ST will prove useful in the future (i.e.
a year or two :-) when there will be faster hard disks around, TOS will (?)
be cleaned-up, and/or the HD will be used with sophisticated disk-caching
software.  (Of course Apple will improve the Mac meanwhile...)

- Moshe Braner