warrenl@graphics.rent.com (Warren Lieuallen) (04/18/91)
I've got an RLL HD controller (and an RLL hard drive, naturally). I'd like to buy another hard drive to add to my system, and have found a good deal, but's it's an MFM drive. The seller suggested that I could simply hook the drive up to my RLL controler and voila, it would now be an RLL drive, instantly upgraded to 7.5 Meg/sec (up from MFM's 5 Meg/sec). Is this true? Can MFM and RLL drives be hooked up inter- changeably? If so, what's the difference between my ST138R and the MFM version ST138? Many thanks!
jcburt@ipsun.larc.nasa.gov (John Burton) (04/18/91)
In article <a1ik13w164w@graphics.rent.com> warrenl@graphics.rent.com (Warren Lieuallen) writes: > > I've got an RLL HD controller (and an RLL hard drive, naturally). >I'd like to buy another hard drive to add to my system, and have >found a good deal, but's it's an MFM drive. The seller suggested >that I could simply hook the drive up to my RLL controler and >voila, it would now be an RLL drive, instantly upgraded to 7.5 >Meg/sec (up from MFM's 5 Meg/sec). > Is this true? Can MFM and RLL drives be hooked up inter- >changeably? If so, what's the difference between my ST138R and >the MFM version ST138? > Many thanks! Yes you can hook an MFM drive up to an RLL controller, and it *should* work...but doing so is like using a 3.5" DD diskette formated for HD, it *should* work but depends on the quality of the diskette (media) and the drive. Generally an RLL rated drive has been designed and tested to more rigid standards since the data *is* stored more densely on the RLL drive (17 sectors/track MFM vs 26 sectors/track RLL). For example with the same drive (an Toshiba MK134R) formatted for MFM will give you ~44MB capacity, formatted for RLL it will have a capacity of ~68MB. So with an RLL drive you get higher capacity and higher transfer rates...unfortunately RLL is slightly more prone to errors... To maximize the probability of successfully using an MFM drive on an RLL controller 1) use a high quality MFM drive - generally drives with voice coil head actuators and thin film sputtered media are a much better choice for this...stepper motor head actuators & oxide media are generally NOT recommended for this type of service...If you want to use a MFM drive with stepper motor & oxide media (most of the low end drives, esp. Segate) in RLL service, well, "you pays your money and you takes your chances..." 2) Make sure your controller cables are in excellent condition (connectors & wires) and be careful with the routing to avoid noise and crosstalk. good luck... John +--------------------------------------------------------------------+ | John Burton | | G & A Technical Software | | jcburt@gatsibm.larc.nasa.gov | | jcburt@cs.wm.edu | | | | Disclaimer: Hey, what can I say...These are *my* views, not those | | of anyone else, be they employer, school, or government| +--------------------------------------------------------------------+
phil@brahms.amd.com (Phil Ngai) (04/20/91)
ins_wayne@actew.oz.au writes: > Let me answer you with a few questions, first: "How much is your > data worth? How much will it cost to recover or replace data > lost from operating a drive out of spec? Will this seller give > you a written guarantee that he will pick up the tab when he Will anyone pick up the tab if you only run it MFM? No. > MFM and RLL drives used to be pretty conservatively engineered. > The MFM drives could be pushed hard. Later, the MFM drives got > "better" and less tolerant of being driven hard. The filters > and logic got "better" and less likely to accept such abuse. Hogwash. RLL does not "abuse" the drive and the concept of being driven hard by RLL is incorrect. -- It doesn't have to be perfect to be useful.
ins_wayne@actew.oz.au (04/20/91)
In article <a1ik13w164w@graphics.rent.com>, warrenl@graphics.rent.com (Warren Lieuallen) writes: > > I've got an RLL HD controller (and an RLL hard drive, naturally). > I'd like to buy another hard drive to add to my system, and have > found a good deal, but's it's an MFM drive. The seller suggested > that I could simply hook the drive up to my RLL controler and > voila, it would now be an RLL drive, instantly upgraded to 7.5 > Meg/sec (up from MFM's 5 Meg/sec). > Is this true? Can MFM and RLL drives be hooked up inter- > changeably? If so, what's the difference between my ST138R and > the MFM version ST138? Let me answer you with a few questions, first: "How much is your data worth? How much will it cost to recover or replace data lost from operating a drive out of spec? Will this seller give you a written guarantee that he will pick up the tab when he *instructs* you to operate it out of spec? To honour the guarantee even though the manufacturer probably won't? Does s/he sign a contract offering to re-enter all your documents and spreadsheets, plus any code you've developed? I doubt it. MFM and RLL drives used to be pretty conservatively engineered. The MFM drives could be pushed hard. Later, the MFM drives got "better" and less tolerant of being driven hard. The filters and logic got "better" and less likely to accept such abuse. The media is another aspect, not to be taken lightly. Frankly, drives are too cheap nowadays to take such needless risks. Lots of people HAVE got away with this kind of thing, but it's like playing Russian Roulette with four bullets. You'll never catch me doing it. > Many thanks! No worries. Shop around. Look for "the last one in the shop" deals and the like, if price is THAT important to you. -- Wayne Myles Email: ins_wayne@actew.oz.au, wsm@ccadfa.cc.adfa.oz.au System Manager, Snail: GPO Box 366, Canberra ACT 2601, Australia. ACT Electricity & Water Ph: +61-6-248-3143 (w) Fax: +61-6-248-3439