Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!ll-xn!ames!ncar!noao!mcdsun!nud!rover!mph
From: mph@rover.UUCP (Mark Huth)
Newsgroups: comp.sys.amiga
Subject: Re: Harddisk for amiga
Message-ID: <775@rover.UUCP>
Date: 29 Apr 88 23:32:34 GMT
References: <2653@crash.cts.com> <27253@aero.ARPA> <925@rmi.UUCP> <926@rmi.UUCP> <252@vedge.UUCP> <1416@ucqais.uc.edu> <519@hechcx.HEC.HARRIS.COM>
Reply-To: mph@rover.UUCP (Mark Huth)
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 21

In article <519@hechcx.HEC.HARRIS.COM> gregg@hechcx.UUCP (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 .

Well, so much for logic.  RLL controllers put 50% more data onto a
given disk than MFM.  MFM encoding essentially uses two baud per bit
to ensure that the clock recovery circuits always have timing
transitions to lock to.  RLL uses an encoding where the length of
successive 0s or 1s is limited so that the clock recovery circuits can
maintain lock, but data is contained in nearly every baud.  RLL stands
for RunLengthLimited.

For RLL to work well, the disk surface usaually has to be somewhat
higher quality - hence a Seagate 238 is an RLL cetified 225.

Mark Huth