Path: utzoo!mnetor!uunet!ncc!alberta!ubc-cs!van-bc!root
From: lphillips@lpami.van-bc.UUCP (Larry Phillips)
Newsgroups: comp.sys.amiga
Subject: Re: Harddisk for amiga
Message-ID: <1740@van-bc.UUCP>
Date: 2 May 88 14:45:20 GMT
Sender: root@van-bc.UUCP
Lines: 41

[please tell me if this line doesn't arrive at your site]

In <519@hechcx.HEC.HARRIS.COM>, gregg@hechcx.HEC.HARRIS.COM (Gregg Asherman) writes:
>MFM is MFM and RLL is RLL
>one controller will not jam any more data on a disk than another controller

>it was written in the previous article that with a 40 meg drive
>and an OMTI rll controller you could get 60 meg
>well, that simply is not logical .

But it is logical. RLL is simply a different way of encoding the data that
allows you to get 50% more data onto the disk.

Example: A Seagate ST225 is a 20 meg drive... 4 heads, 613 cylinders,
         A Seagate ST238 is a 30 meg drive... 4 heads, 613 cylinders.

They only differ in that the ST238 is 'RLL certified', and has been tested
for its data integrity at the higher flux change rate. Normally, RLL drives
use plated media and/or better heads to handle the density. An MFM drive
that holds 40 megs can be formatted to 60 megs using an RLL controller, but
it will tend to be unreliable, and often will start losing data in time
(time being anywhere from minutes to weeks). Similarly, a 60 meg RLL drive
can be formatted with an MFM controller, resulting in a 40 meg drive.
Though this is more reliable, some manufacturers recommend not doing it.
Seagate apparently goes so far as to say that using one type of drive with
the other type of controller will void your warranty.

Summary: The controller determines the amount of data on the drive.

-larry



--
Janus? Well, look at it this way. If you squint a little, the J could be
       Amiga checkmark, and the rest of the word describes MsDos.
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|   //   Larry Phillips                                          |
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