MFM controller cards

I just did an ebay search and came up with more than 30 various MFM controllers, most are pretty cheap.

Ask your local computer recycler to look out for one for you.

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You may be able to find a MFM controller, but it may not work with any of the mother boards past the 368 or 486 era.

As for the new mother boards, the expansion slots would not be compatible, and also the BIOS may not see the MFM controller.

What I would do, is get an older working computer that has MFM drive support, and put everything to floppies to transfer it across. Networking a very old dos computer to a Windows based computer may not be worth the effort.

I would be curious to know why you did not have everything backed up on floppies or something in the first place?

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JANA _____

Before you buy, why do you think the controller has gone bad? In a system old enough to use MFM drives there could be a lot of reasons for a problem. What's the system doing or not doing? Any POST error codes?

Have you tried the obvious first? Pulled the conroller card, cleaned the card contacts and reseated the drive cables? You may want to clean the contacts on the drives too - considering they use card edge connectors.

Rick

Hi!

Good points, all of them. Checking to be sure that the system's CMOS battery is still running would be an excellent idea. After years of sitting it could be dead or depleted. (Many older motherboards used a rechargeable NiCad "accordion pack" battery.) If yours has a battery like this, leaving the system powered on overnight might bring it back up. They do seem to be pretty robust.

Be ***very*** careful if you do this! If you can help it, do *not* remove those hard drives from the system unit. ST-251 drives have stepper motor head actuators that are subject to falling out of calibration with the information stored on the drive platters if the operating temperature range changes or the drive is removed and reinstalled. There are only two ways out of this if you get the drives working--either hope that you can find the right climate/installation "sweet spot" or low-level formatting. Low level formatting will destroy all data on the drives.

William

Can you cite a reference? In my experience, MFM drives are about the most robust things on the Planet. :) The tracks are so far apart that normal temperature changes have no effect. I have some ST-251s (I think that is the model) sitting at the bottom of a closet. I bet if I could find a system today to power them up, they would work just as well as

20 years ago (if the grease hasn't congealed).

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Hi...

Anyone else remember "stiction" ?

Take care.

Ken

Sure. It started out on 40meg Quantum brand 3.5inch SCSI drives. Due to the quickly changing technology, Quantum got as far as the LPS (Low power) 105 meg drives before they found out about the problem and replaced the grease.

I've heard of a few 20 meg drives having it, but have never seen one.

Where there other manufacuters?

As far as I know, it never affected MFM/RLL/IDE drives.

That was in the early 1990's. By now, most drives of that age of any type and manufacturer may be afflicted by it.

Geoff.

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I agree, I've a few of them, WD 20Mb and a Kalok 40 Mb with Win3.11, no defective sectors. These disks never die.

That's not the way I understand the technical problem. Physical removal of the drive doesn't do anything. It's actually operation of the drive that can eventually cause problems. Considering how much heat these drives generate during operation simple temperature changes from removal/reinstallation aren't going to cause the problem.

Because the stepper motors aren't all that accurate for head placement, over time data is written not quite exactly in the same position on the physical tracks. If the variance is bad enough over time you can start getting "sector not found" errors and the like if the write position for the data gets too far out of alignment with the servo tracks. It can start crapping out the servo tracks in the process - making head placement impossible.

The cure is to just perform a low level format on MFM drives with stepper motor head actuators every few years as part of routine maintenance, rather than wait for read or write errors to start happening. And, of course, back it up and make sure you have a reliable restore procedure before doing this.

The problem does not apply to MFM drives with voice coil head actuators.

Rick

On Mon, 26 Feb 2007 14:34:23 GMT, Ken Weitzel put finger to keyboard and composed:

The following article suggests that stiction is a problem that first appeared in 3.5" drives.

"In the context of hard disk drives, stiction refers to the tendency of read/write heads to stick to the platters, preventing the disk from spinning up and possibly causing physical damage to the media. Some hard drives avoid the problem by not resting the heads on the recording surfaces.

Stiction is also known to cause read/write heads to stick the platters of the hard drive due to the breakdown of lubricants which coat the platters themselves. In the late 1980s and early 1990s as the size of hard drive platters decreased from the older 8" and 5.25" sizes to

3.5" and smaller, manufacturers continued to use the same calendering processes and lubricants that they had used on the older, larger drives. The much tighter space caused much higher internal operating temperatures in these newer smaller drives, often leading to an accelerated breakdown of the surface lubricants into their much stickier components."

- Franc Zabkar

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Yep, been there done that. :) A good whack on one corner was one method!

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I used to have a 286 with one of those, I used it for years after removing the cover to break free stiction so it would spin up and it never failed.

Unfortunately the similar 30MB RLL drive in my PC/XT died, I dragged it out of long term storage in my mom's shed and it makes some unhealthy noises and won't boot :(

Stiction was caused by the read/write heads getting stuck to the disk surface. For years I had an open 20MB Seagate SCSI drive sitting on my bookshelf, one day I rotated the platter by hand and it ripped a couple of the heads right off the arms, they were stuck quite firmly to the disc. Oops!

I also remember (but never tried) the idea of putting the drive in the freezer for a while in a plastic bag and letting the temperature change do the work. (The plastic bag was to reduce condensation on the drive itself.)

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You're sure it was MFM? The 251's were often used with RLL controllers.

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The US Post Office should just raise postage rates by two dollars an ounce
with the promise that they won't raise rates for at least a week. They'll
never go for it; they couldn't possibly wait a whole week.

People often "cheated" and used MFM drives with RLL controllers, but the ST-251 was designed as a 40MB MFM hard drive. It was original equipment in the IBM AT.

'Often used' are the key words here, the 251's were MFM but worked fine with an RLL controller thus acquiring a bit more storage space.

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