skrenta@eecs.nwu.edu (Richard Skrenta) (02/08/89)
I've got a Miniscribe 6053 (40 meg) and a Seagate ST-4096 (80 meg) on a standard Western Digital MFM controller. I've heard that switching to an RLL controller could boost the available space on each drive by 50% as well as increasing the data transfer rate. Are there any dangers associated with using an RLL controller on drives only certified for MFM? Could the controller damage the drive in any way, or is it just a matter of mapping a few more bad tracks during the format? I noticed there are some nasty warnings in the Seagate manual about voiding your warranty if you use the wrong controller with a drive. Also, where does the extra space come from? Do RLL controllers increase the sectors per track or the number of tracks? How would I get Xenix to recognize the new space? Any advice would be appreciated, Rich Skrenta -------------------------- skrenta@gamma.eecs.nwu.edu
karl@ddsw1.MCS.COM (Karl Denninger) (02/09/89)
In article <3700022@eecs.nwu.edu> skrenta@eecs.nwu.edu (Richard Skrenta) writes: >I've got a Miniscribe 6053 (40 meg) and a Seagate ST-4096 (80 meg) on a >standard Western Digital MFM controller. I've heard that switching to >an RLL controller could boost the available space on each drive by 50% >as well as increasing the data transfer rate. Yep. If your board can handle the increased transfer rate (WD1006-VSR2), or has a true track buffer, you'll get much higher throughput. The basic data rate is 750kbytes/second rather than 500kbytes/second as with MFM. HOWEVER: A cheap RLL board will only give you increased capacity, not performance. Ask the magic question: "Is it truly track buffered"? >Are there any dangers associated with using an RLL controller on drives >only certified for MFM? Could the controller damage the drive in any >way, or is it just a matter of mapping a few more bad tracks during the >format? I noticed there are some nasty warnings in the Seagate manual >about voiding your warranty if you use the wrong controller with a drive. I've never seen a drive that was physically damaged by RLL formatting. You may find some, particularly older drives with non-plated media, that won't work with RLL formatting. There are a few that will appear to work, but won't hold up over time; that is best checked out with a thorough diagnostic or some analog equipment. Some controllers have on-board surface analysis software that does a _real_ good job, the WD1006VSR2s come to mind again. The Adaptec's surface scan is just a read/write test from what I can tell. If you run a "dos level" surface analysis utility, let it run 48 hours at a _minimum_ with worst-case patterns before you say everything is ok. I've never had a problem with RLL as long as I do the surface analysis and make sure that I've got all the bad areas locked out. Seagate doesn't like people knowing that many of their drives are the same in both RLL & MFM configurations (they sell both; RLL is more expensive), so they put those nasty warnings in the manual. In reality, if you were to reformat with MFM they'd never be able to tell you ran RLL format...... The only time it would be an issue is if the drive were to fail catastrophically but in such a manner that Seagate could determine the format later (but I hear rumors that they don't inspect or check returns anyways......) >Also, where does the extra space come from? Do RLL controllers increase >the sectors per track or the number of tracks? How would I get Xenix to >recognize the new space? They run 26 sectors per track instead of 17; this is why some drives don't work. The density of information on the tracks is raised by 50% to accomplish the increased storage; this means the drives must be able to resolve a "smaller" magnetic domain (and write a smaller one too). Most current drives _are_ up to the requirement. We've been using two of 'em in our Xenix machine now for about a year and a half with no trouble at all (ST4096 and ST251). If you're paranoid you can pay Seagate to guarantee that the ST4096 you get will work with RLL, the only difference is that the model number then is "ST4144" and you get to pay more money; the same trick can be pulled with a ST251 (you buy an ST277 instead) Other than the certification level, there is no difference between these drives. :-) Disclaimer: We sell track-buffered RLL controllers, as well as MFM boards. Of course I'm biased, but we do put our own data on our internal systems where our mouth is. :-) My understanding and personal experience is that the following tend to work: Seagate: ST4096 (late models) ST251-x (for any value "x", as long as it's a suffixed drive with an "MLC" sticker it should be ok) ST225 (some; I wouldn't trust these!) Maxstor: XT1140 (most units) XT2190 (Nearly 220MB formatted! Yikes! Once again, most units) RLL certified drives are also available from Maxstor. CDC WREN: Some Wren IIIs (not all) will work. Priam: Most models, the ID-xx series are usually ok, some are certified. Miniscribe: Most 60xx series work fine (plated media and whitney actuators are probably responsible here). Check older units in particular! -- Karl Denninger (karl@ddsw1.MCS.COM, ddsw1!karl) Data: [+1 312 566-8912], Voice: [+1 312 566-8910] Macro Computer Solutions, Inc. "Quality solutions at a fair price"
tissot@nicaud.UUCP (Kevin Tissot) (02/10/89)
skrenta@eecs.nwu.edu (Richard Skrenta) writes: > .... I've heard that switching to > an RLL controller could boost the available space on each drive by 50% > as well as increasing the data transfer rate. True. > Are there any dangers associated with using an RLL controller on drives > only certified for MFM? Could the controller damage the drive in any > way, or is it just a matter of mapping a few more bad tracks during the > format? The controller should not damage the drive in any way. Your data, however, may not be so lucky. Using an RLL controller on an MFM drive may lead to data loss since the RLL format places higher demands on the disk media than the MFM format does. Some drives can handle this and some can't. My guess would be that your Miniscribe disk might work but your Seagate will probably fail miserably. > Also, where does the extra space come from? Do RLL controllers increase > the sectors per track or the number of tracks? Most PC RLL controllers increase the sectors/track from 17 to 26, thus increasing both the data storage capacity and the raw transfer rate from the media to the disk head. Whether or not this increases the transfer rate to your PC depends on the disk controller you choose. A good controller which supports 1:1 interleave will give the best improvement. -- Kevin Tissot / /~~~\ \ Nicolet Audiodiagnostics /|/ O O \|\ Madison, Wisconsin \|\ _ /|/ ...uwvax!astroatc!nicmad!nicaud!tissot \___/
kory@avatar.UUCP (Kory Hamzeh) (02/11/89)
In article <3700022@eecs.nwu.edu>, skrenta@eecs.nwu.edu (Richard Skrenta) writes: > Are there any dangers associated with using an RLL controller on drives > only certified for MFM? Could the controller damage the drive in any > way, or is it just a matter of mapping a few more bad tracks during the > format? I noticed there are some nasty warnings in the Seagate manual > about voiding your warranty if you use the wrong controller with a drive. Do NOT use MFM drives with a RLL controller. I am speaking from very bad experience. I bought 2 Rodime RO3055 drives and where told by the dealer that these drives are RLL. Being the trusting kinda fella that I am, I didn't bother to check with Rodime. Well, the drives worked flawlessly for the first month or two. After that, I would start getting a new bad sector a day. It got to the point that the drives were not usable. Reformatting helped a bit, but the problems would re-appear in about a month later. I assumed that just because the drives where plated, they were RLL compatible. Wrong assumption. The drives MUST be RLL certified by the manufacturer. > Also, where does the extra space come from? Do RLL controllers increase > the sectors per track or the number of tracks? How would I get Xenix to > recognize the new space? The extra space come from the fact that RLL controllers use a different encoding technique which allows them to basically compress more data on each track. There are two different encoding methods. One methods increases your capacity by 50% and the other by 100%. When the controller is initialized, it over write the standard drive table with its own. Xenix will read this table during installtion. I use the Adaptec controller (ACB2732???) and have had absoulutely no problems with Xenix or Mess-Dos. I would like to hear from people that use the 100% increase controller. Who's controller and drive are you guys using? --kory -- ------------------------------------------------------------------------------- Kory Hamzeh UUCP: ..!uunet!psivax!quad1!avatar!kory INTERNET: avatar!kory@quad.com
skrenta@eecs.nwu.edu (Richard Skrenta) (02/14/89)
I asked "Can you use a RLL controller on MFM drives?" I was asked to post the responses I got to this question, so here they are. Overall, the picture is mixed; I haven't come out with any clear conclusion. Some people report extra disk space, faster access and no problems. Others tell horror stories. It's probably not a good idea for the faint-of-heart or those who can't afford to blow the extra bucks on a wasted RLL controller, assuming it doesn't work. Rich Skrenta ----------- From: Chip Rosenthal <chip@vector.uucp> In article <3700022@eecs.nwu.edu> you write: >Are there any dangers associated with using an RLL controller on drives >only certified for MFM? I classify this question in the same catagory as: - Can I run an 80286-8 at 10MHz. - Can I use 21256-120 RAMs at 100ns. RLL encoding is "denser", thus you get 26 (512-byte) sectors on each disk track rather than 17. Can the surface of your disk handle the higher density? At nominal conditions, probably. At the extremes, all bets are off. A lot of people do run MFM-rated disks with RLL controllers. And a lot of people do stuff 8MHz CPU's in 10MHz systems. My paranoia about doing this is because I used to be a test engineer, and I wrote test programs which do the speed gradings for CPU's. Think about it...a manufacturer loses money when a piece of hardware is sold as the lower performance grade. If it could, it would rather classify the thing as RLL or 10MHz or 100ns and charge the increased price. >Could the controller damage the drive in any way No. The risk is of lost data. >I noticed there are some nasty warnings in the Seagate manual >about voiding your warranty if you use the wrong controller with a drive. 1. They don't want to be responsible for lost data. 2. They want you to buy the more expensive (RLL) disk. >Also, where does the extra space come from? Writing more sectors in the same amount of space. >Do RLL controllers increase >the sectors per track or the number of tracks? Sectors per track. >How would I get Xenix to recognize the new space? Through the "dparam" program, with which you define all of the characteristics of the drive. >Any advice would be appreciated Running a MFM disk on an RLL controller will probably work. The question is, do you want to take the gamble. --- Chip Rosenthal chip@vector.UUCP | Choke me in the shallow water Dallas Semiconductor 214-450-5337 | before I get too deep. -------- From: "M.R.Murphy" <mrm@sceard.uucp> [...] An Adaptec 2372 didn't work with ST251, ST251-1, or ST4096. Many errors on drives that worked fine MFM. They worked again fine MFM when I switched controllers again. I found out the hard way. Would you summarize to the net? Regards, Mike --- Mike Murphy Sceard Systems, Inc. 544 South Pacific St. San Marcos, CA 92069 mrm@sceard.UUCP {hp-sdd,nosc,ucsd}!sceard!mrm +1 619 471 0655 ------------ From: tony%ajfcal%xenlink%calgary%uw-beaver%rochester%ames.uucp%mailrus.cc.umich.edu@cs.umn.edu The Segate 4096 DOES work correctly in RLL mode on Xenix. I think the Miniscribe might also. Almost any drive using "plated media" disks, (e.g. Segate 4909, all Priam's etc.) can be used in RLL mode. These have a flux density rating of at least 10,000 (i.e. coercivity, i.e. a measure of the energy needed to magnetize). In general, the older red oxide disks cannot be used for RLL - in part because of the low coercivity). (Note. An issue of Byte just came by mail with an article on RLL. This might give a better description than mine. But i have not have time to read it.) [ I went out and got this issue of Byte. The article is very informative, it tells all about RLL. However, it doesn't say much about using MFM drives with RLL encoding -- Rich ] The "certification" process used by the manufacturers is designed to determine the number of defective tracks on the disk. If the disk is to be used for RLL, then the certification is done with an RLL tester; if for MFM, it is done with an MFM tester. In general, the manufacturers select the "best" disks for RLL certification - and therefore command a higher purchase price. RLL does give noticable increase in performance. You are now recording 26 sectors per track instead of 17. In one disk revolution, you can now (at least theoretically) pick up more information in one revolution. On the whole, I notice an improvement in speed as well as storage capacity. I currently have two 4096 drives and two Priam ID60's. All of these were "certified" for MFM, however work verrrry fine in RLL. To use your segate 4096, the following should be done: 1. format the disk in RLL format, using a formatter such as SPEEDSTOR - setting the "number of sectors per track" to 26. 2. run an overnite media check on the 4096 to pick up all possible bad tracks. Remember that the drive was certified for MFM. If it is used for RLL, a couple of extra bad tracks may be found in the testing (None of my drives had additonal bad sectors...). 3. Install Xenix. Modify the hard disk parameters to indicate that the number of sectors per track is 26 (not the normal 17 for MFM). 4. Run the Xenix "media check" just to make sure. 5. continue with the installation as normal. tony.... --- +------------------------------------ | Tony Field ..alberta!calgary!ajfcal!tony | Co-Design Information Systems Ltd. | Calgary, Alberta, Canada voice: (403) 266-3239
davidsen@steinmetz.ge.com (William E. Davidsen Jr) (02/15/89)
In article <3700022@eecs.nwu.edu> skrenta@eecs.nwu.edu (Richard Skrenta) writes: | Are there any dangers associated with using an RLL controller on drives | only certified for MFM? Could the controller damage the drive in any | way, or is it just a matter of mapping a few more bad tracks during the | format? I noticed there are some nasty warnings in the Seagate manual | about voiding your warranty if you use the wrong controller with a drive. You are going to get a lot of answers to this, let me supply some information which will help you put it all in perspective. RLL controllers don't "put the bits closer together" in terms of more flux changes per inch (fpi) on the media surface. What changes is the resolution of the changes in terms of time. In order to run RLL on a drive and controller combination successfully, the total timing jitter or resolution from end to end must be less than some value N in ns. If you look at the drive test sheets you may see a jitter number for the drive. If you get a chance to select a drive from a batch, take one with a small number, since this gives you a margin of error with any drive. RLL certified drive are *usually* production MFM drives which have been tested for media quality and jitter, and found to be good enough to run RLL. There are probably some manufacturers who make a whole diferent disk, but I have yet to identify one. This menas that when you get an MFM drive it may be one which didn't work as RLL, or it may be one which wasn't tested, or it may be one which passed but wasn't sold because more RLL capable drives were made than were needed to fill orders. With prices down manufacturers don't keep too many drives in stock, and will sell the RLL tested drives under the MFM label. Controllers have an acceptable range, just like drives, and one which is acceptable may barely pass the specs or be 20-30% better (smaller) in jitter. If you get a "real good" controller you can run some pretty bad disks, as long as the total jitter is acceptable. TOTAL JITTER - drive 1) rotational speed varitions a) motor b) drive train c) bearing drag 2) media a) type b) quality of application 3) heads - manufacturing tolerances 4) electronics a) response time (slew rate) of amplifiers b) voltage regulator output c) component manufacturing tolerances d) quality of edge connection TOTAL JITTER - controller 1) electronics a) response time (slew rate) of amplifiers b) voltage regulator output c) component manufacturing tolerances d) quality of edge connection TOTAL JITTER - other environment 1) quality of power supply output a) voltage b) ripple c) spikes 2) cooling a) average temperature b) temperature fluctuations c) humidity 3) other a) magnetic fields b) vibration (affects mechanical connections) c) user practices - frequent power on, etc We are talking ns tolerances here, so it doesn't take too much to change things. WHY ALL THE DIFFERENT RECOMMENDATIONS? If someone has a marginal controller (at the limit of whatever the manufacturer allows for jitter), it will take a reasonably good disk and environment to keep operation reliable. Couple this with some MFM disks which are a little wide on tolerance and "I tried and MFM disks just don't work as RLL." Note that the person with a very tight tolerance controller may report "MFM works fine, I've used any number of 'em." Both of these people are giving you their best advice, and you should be thankful they share their experience with you. If a combination is marginal a number of things will help: temperature should be kept as even as possible. When I first went RLL I had one disk which would run for a few weeks and then get more and more bad sectors. I finally noted that it failed right after I powered up. Solution? Wait 15 minutes after power on to run anything which might write to the disk. A friend had a disk which failed when he played one game... he was leaning the map against the front of the computer case and partially blocking the airflow. RLL WILL DESTROY YOUR DISK If you format RLL and it doesn't work out, the drive must be low level formatted with an MFM controller before reuse. Virtually all of the stories originate with someone who tried to do a DOS (high level) format and failed, concluding that the disk was broken. Some controllers seem to be unable to do a low level format for some reason, and this would make them unable to reformat a disk which had been used as RLL. I have only seen one case where a drive could not be reformatted on a known good controller, and that one suffered a massive mechanical failure of a bearing. IT WORKS FOR A FEW WEEKS AND THEN GRADUALLY GOES BAD This *usually* means you have not locked out all of the bad tracks. I've had this happen myself, and it was usually cured by locking out just a few tracks. It seems that under both DOS and Xenix a few unmapped bad sectors cause additional problems. I can't explain it, just observation, if it doesn't start it doesn't spread. Also, disks running RLL definitely do go bad with use. So do MFM disks, cars, trains, and people. Everything wears out, and a failure after several years doesn't mean that RLL has warped your bits. The only that which gets better with time is wine. WHAT TO DO? If you can find a dealer who is understanding, you will probably be able to get a 10 day return on a controller (that dealer may not be the cheapest price in town). When you low level format run the surface test(s) for 3-4 hours, and be sure to let the disk warm up for 15-20 minutes before formatting. If the test can be run continuously, run them for a few days! If you get vast numbers of errors, you may just have a combination which doesn't work. Anyone who claims that any MFM drive will work "all the time" as RLL probably is an optimist. You can save a lot of money by using MFM drives with an RLL controller. In most cases they will work, and reliably. Even going with a high cost RLL drive from a big-name manufacturer will not absolutely insure that you get reliable operation (it does improve the chances, though). I have had good drives not work, and a number of cheap Seagates work for years. I have used RLL and even the Perstor ARLL (90% increase) controllers on MFM drives without trouble. If you can afford to go top drawer all the way, buy all RLL components (or better yet, ESDI). If you can't afford the money to take some risk that the combination won't work, don't even try it. If you fall in the middle (most of us do), give it a try, if you install it carefully the odds are in your favor. An Adaptek controller is about $150 (back of PC Week) and the WD is about $250. There are others in between. Most of them are less than the diference between an MFM drive and the same drive rated RLL, and easier to install. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me