ang@valhalla.ee.rochester.edu (10/26/88)
I am planning to buy a Miniscribe 60 MB 1/2 height (61 ms, RLL) from Compuadd (mail order firm based in Texas) for my Leading Edge Model M PC. The configuration of my machine is as follows: - 8088-2, 640 K RAM -two floppy drives (no hard disk controller - 1 serial, 1 parallel port - CGA card with RGB monitor - 135 watt Power supply - hardware switch selectable at 4.77 MHz or 7.16 MHz - running Leading Edge MS DOS 2.11 - ROM Bios Version 2.10 dated 01/01/85, by Mitsubishi Electric I have no room for the hard disk so I plan to remove one of my floppy drives. I need your advice regarding the following: 1. I have recieved information than RLL controllers are VERY unreliable, to the extent that they need to be serviced (with the drive) every year. Is this true ? I was told to stay way from them and just use the "MFM" controllers. 2. Will my ROM bios allow me to access this 60 MB disk? Will there be problems with running "partitioning software" with my bios? Will I be able to boot from the hard disk? Any advice/comments will be very much appreciated. Please e-mail me directly. (I was not able to get any info from Leading Edge since they don't manufacture this computer anymore -> that's product support for them!?!?) Marcelo H. Ang Jr. Department of Electrical Engineering ang@galaxy.ee.rochester.edu ang@ee.rochester.edu
ads4@tank.uchicago.edu (adam david sah) (10/30/88)
RLL IS unreliable now. Now only because the new generation of machines has higher clock speeds, which exceed the capability of RLL controllers to necessarily encode the data fast enough. One friend of mine had to slow down his AT from 12mhz to 6mhz in order to ensure 100% writing! The results previously were disastrous. If anyone can confirm this, please reply publicly! -A.Sah'88
chasm@killer.DALLAS.TX.US (Charles Marslett) (10/30/88)
In article <584@tank.uchicago.edu>, ads4@tank.uchicago.edu (adam david sah) writes: > RLL IS unreliable now. Now only because the new generation of machines has > higher clock speeds, which exceed the capability of RLL controllers to > necessarily encode the data fast enough. One friend of mine had to slow > down his AT from 12mhz to 6mhz in order to ensure 100% writing! The results > previously were disastrous. If anyone can confirm this, please reply publicly! > > -A.Sah'88 The problem your friend had is probably due to the controller card not working properly with the bus speed (as you mentioned), but that has very little to do with the drive data encoding algorithms. His best bet to find a controller that works well at the full bus speed is to get one reccommended by the motherboard manufacturer or to try a brand new this year super duper bang up expensive controller (I don't know what the current one is . . . (;-). Seriously, RLL controllers are almost always faster than the MFM ones (and slower than the EDSI drives most of the time, too). They are more often buffered which also speeds them up, and they are newer technology also speeding them up. As a result, they are often configured to run with reduced wait states and this will lead to problems if the motherboard is running significantly faster than an 8 MHz AT -- Everex Step machines are especially bad (good?) in this respect because they also run a funny symmetry clock as well. A possibility is that the RLL controller can be reconfigured for standard numbers of wait states in this case. In conclusion, RLL controllers are about as likely as any others to fail in any particular machine -- but the box maker or the RLL card maker should know enough to offer some reccommendations and/or offer some kind of fix. Charles Marslett STB Systems, Inc. <-- apply all standard disclaimers, we are not chasm@killer.dallas.tx.us in this business yet!
jmj@mhuxu.UUCP (J. M. Johnson) (10/30/88)
In article <584@tank.uchicago.edu>, ads4@tank.uchicago.edu (adam david sah) writes: > One friend of mine had to slow down his AT from 12mhz to 6mhz in order to > ensure 100% writing! The results previously were disastrous. If anyone > can confirm this, please reply publicly! I had some difficulty with installing an ST238 and RRL controller in a Computerland BC88. The machine would frequently come up with parity errors while running at 8MHz. I had to slow the system to 4.77MHz so that everyone would play nicely together. Other than this problem, everyone was quite happy with the new disk. -- Life's just a game, you fly a paper plane, there is no end. - TBA J. M. Johnson, AT&T Bell Laboratories, Reading, PA ...!att!mhuxu!jmj
jborza%burgundy@Sun.COM (Jim_Borza) (11/01/88)
In article <584@tank.uchicago.edu>, ads4@tank.uchicago.edu (adam david sah) writes: > RLL IS unreliable now. Now only because the new generation of machines has > higher clock speeds, which exceed the capability of RLL controllers to >necessarily encode the data fast enough. One friend of mine had to slow >down his AT from 12mhz to 6mhz in order to ensure 100% writing! The results >previously were disastrous. If anyone can confirm this, please reply publicly! > I don't think it is RLL which is unreliable. The existence of an RLL-encoded disk is not (necessarily) apparent to the CPU except in the increased number of sectors-per-track. The type of encoding (MFM or RLL) is only an issue between the controller and the disk drive. As with nearly all PC peripherals, some controller cards are more adaptable than others, particularly in their ability to run with different bus speeds. If I were to hazard a guess, I think your friend's problems were caused by the controller card and its interface with the bus. Some cards provide track buffering and other features to improve performance and reliability. Many are low-cost clones designed for a limited performance range and get caught up when the user is smarter than they are. Another problem lies with many (not all) expansion card manufacturers' re- luctance to distribute specifications and schematics with their hardware. Bottom line: RLL is a proven encoding scheme which provides higher den- sities than MFM with a larger base of drives than many manufacturers are willing to admit. There are many more variables to contend with external to the encoding scheme in the typical PC/AT system. Jim Borza Communication Factors - Fremont, CA (415) 797-3039 Sun Microsystems - Milpitas, CA
del@Data-IO.COM (Erik Lindberg) (11/01/88)
In article <584@tank.uchicago.edu> ads4@tank.uchicago.edu.UUCP (adam david sah) writes: >RLL IS unreliable now. Now only because the new generation of machines >has higher clock speeds, which exceed the capability of RLL controllers >to necessarily encode the data fast enough. One friend of mine had to >slow down his AT from 12mhz to 6mhz in order to ensure 100% writing! >The results previously were disastrous. If anyone can confirm this, >please reply publicly! > >-A.Sah'88 This is ridiculous! (No offense to you, Adam) *ALL* 286 machines run faster than the data encoding to disk. It is the function of the controller to signal the CPU when it is ready to receive the next byte. The CPU simply waits until the controller is ready. Your friend had a poorly designed (or defective?) disk controller that could not run AT THE BUS INTERFACE LEVEL at the 12 mhz speed. It didn't happen to be a Western Digital controller, did it? -- del (Erik Lindberg) uw-beaver!tikal!pilchuck!del
davidsen@steinmetz.ge.com (William E. Davidsen Jr) (11/04/88)
In article <584@tank.uchicago.edu> ads4@tank.uchicago.edu.UUCP (adam david sah) writes: | RLL IS unreliable now. Now only because the new generation of machines | has higher clock speeds, which exceed the capability of RLL controllers | to necessarily encode the data fast enough. One friend of mine had to | slow down his AT from 12mhz to 6mhz in order to ensure 100% writing! | The results previously were disastrous. If anyone can confirm this, | please reply publicly! Wrong. Some controllers do not run at very high bus speeds. As a general rule I regard any controller which won't run at least 8MHz bus to be a poor design, and any clone which runs the bus faster than 8MHz (not the CPU, the bus) to be suspect with many cards. If the clone is running the bus at full speed, there are a LOT of cards which don't work that fast. In any case I have used Adaptec and PerStor controllers in my system, a 16MHz 386 with 8MHz bus. Both have worked fine. I see no problems with RLL, although some RLL controllers might have a problem. There are a lot of MFM controllers which don't run above 8MHz bus, too. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me