Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!ginosko!usc!orion.oac.uci.edu!mrichey From: mrichey@orion.oac.uci.edu (Mike Richey) Newsgroups: comp.sys.ibm.pc Subject: Re: RLL controllers with MFM drives Message-ID: <3544@orion.cf.uci.edu> Date: 23 Oct 89 18:02:19 GMT References: <2546@bingvaxu.cc.binghamton.edu> <4265@ncsuvx.ncsu.edu> <35883@srcsip.UUCP> <4273@ncsuvx.ncsu.edu> Reply-To: mrichey@orion.oac.uci.edu (Mike Richey) Organization: University of California, Irvine Lines: 78 In article <4273@ncsuvx.ncsu.edu> unkydave@shumv1.ncsu.edu (David Bank) writes: > > ,. In response to Brynn Roger (rogers@src.honeywell.com): > > Nope. I don't sell hard drives. I merely install and maintain >them and diagnose them when they go bad. > Contrary to your assertion, plated media is NOT the sole >basic difference in RLL-rated drives. The biggest single difference >is in the use of VOICE COIL technology in the armature control >mechanism. This is what allows the mush more closely controlled >head movement demanded by RLL. The plated media simply makes >for a more reliable rusty pie plate. This is not true. The difference between the ST225 and the ST238, the miniscribe 8425 and 8438 is certainly not plated media any more, but whether or not in the factory it passed the RLL tests. Neither of these drives has a voice coil. RLL PUTS NO MORE BITS ON A SURFACE than MFM. the DIFFERENCE is the 2,7 ENCODING -period-. > Sure, I know people running MFM drives on RLL too. Its >like the car you drive off the lot and it never needs to see a >mechanic. Some RLL drives are just able to do it. You may be running >them at the edge of tolerance, but you are just on this side of >their operational capacity. I never meant to say it was IMPOSSIBLE >to run an MFM drive on RLL. Merely dangerous with your data. > RLL has been aound for a very long time. It has been used with mainframe drive systems since the early seventies. It's only recently that RLL came to the PC market (like 1984). Rodime made a number of drives (some that had plated media, some that didn't) that were NOT rated for RLL, that simply worked with RLL. Novell used to sell the Maxtor XT1140 hard disk drive in their NDS-2 and NDS-4 hard disk subsystem. This drive enclosure included a SCSI (Adaptec 4070a) that had an ST412 interface that used RLL encoding. The Maxtor XT1140 is not or ever has been RLL spec'd. There were a series of tests that Novell would run and these tests were distributed with Netware to make sure the drive that was installed was capable of handling RLL encoding. The installer was encouraged to run these legthly tests on a drive that was to be installed. Know what, I've got dozens of these drives on sites that have been going for >3 years, without a bit of trouble. In fact, Maxtor began marketing a drive called the XT1240, that was an RLL certified XT1140. Same drive, Same logic, same everything. Well different serial number. One of the differences from drive to drive is a device known as the pulse detector. This device sits on the read/write head. It detects the flux pulses that pass under it from the surface of the disk. This device is a very important one. Silicon Systems is the company that supplies them to Seagate and Miniscribe. The one that's used in the ST225 and the ST238 is not a current design. Silicon Systems still manufactures it specifically for Seagate. Silicon Systems doesn't support the part anymore and has advised Seagate to change the design because of faults that S.S. has fixed in newer designs. But, Seagate uses the old one. Why? because the newer one probably costs .12 more (my opinion). This little device is suspect of causing intermittant problems with the ST225s and ST238s that drives sometimes experience. I've had problems with ST2XX series where low level formatting fixes the intermittant problems (or spinrite). Well, without rambling on anymore...... Seagate tests all of their ST225 and ST238 drives at RLL first. If they pass RLL, they're ST238s, if they fail, they test tham at MFM and ship them as ST225s if they pass. This information I was told by seagate. This only make economic sense if not logical. Hey, you have a lot to offer, but no one is an expert on anything. No matter how much you know, there's always some smart@ss out there that thinks they know more 8-). So lighten up. And have a good today. Michael S. Richey Internet: mrichey@orion.oac.uci.edu Bitnet: MRichey@UCI CompuServe: 71650,3132 Voice: (714) 856-8374 University of California, Irvine Network and Telecommunications Services 342 Computer Science Irvine, CA 92717