From: frizzle@tx.rr.com   
      
   Knut wrote:   
   > On 07.04.2010 01:30, Charles Richmond wrote:   
   >> Knut wrote:   
   >>> On 01.04.2010 19:04, Herbert Johnson wrote:   
   >>>> On Apr 1, 7:17 am, (Bill Gunshannon) wrote:   
   >>>>> "Wesley" writes:   
   >>>>>   
   >>>>>> If you can come up with something practical and inexpensive to   
   >>>>>> connect an   
   >>>>>> IDE drive to a computer with an ST-506 (assuming here that ST506 =   
   >>>>>> MFM)   
   >>>>>> interface, you would have some interested folks.   
   >>>>>   
   >>>>> If it were doable at all, it would be so complicated you might as well   
   >>>>> just use another computer. There is nothing common at all between the   
   >>>>> two interfaces. Easier to throw out the ST506 card and just interface   
   >>>>> to the bus of the computer.   
   >>>>>   
   >>>>> bill   
   >>>>   
   >>>> From my experiences in the XT/AT era, MFM drive formats were not   
   >>>> consistent from controller to controller brand/model. A drive used   
   >>>> with one brand/model MFM controller, was not readable by another.   
   >>>> People today are used to moving IDE/ATA or SATA drives around without   
   >>>> problems. They think "if it fits, it ships" - that is, if you can   
   >>>> connect computer A to thing B, "the computer" can read it. Not so, in   
   >>>> 1980's and earlier computing. So, even a direct interface would be a   
   >>>> problem, one of proper format, possibly even "low level" format too.   
   >>>>   
   >>>> herb johnson   
   >>>> retrotechnology.com   
   >>>   
   >>> The MFM controller is a very different beast from IDE. An MFM   
   >>> controller needs to be paired with the drive. This is done by low   
   >>> level formatting the drive. It is actually advised also to low level   
   >>> format the drive regularly (would be done with tools like spinrite).   
   >>> This is so because timing critical components are on the MFM controller.   
   >>>   
   >>> The trick they did with IDE was to move all the timing critical stuff   
   >>> onto the drive and to recalibrate without needing the user to initiate   
   >>> it. Therefore the IDE interface is quite simple and the drive will   
   >>> work with (almost) any IDE interface...   
   >>>   
   >>> For a while there were also RLE drives, these were better MFM drives   
   >>> utilizing run-length-encoding so data was compressed on the drive. One   
   >>> shouldn't low-level format RLE drives either.   
   >>>   
   >>> We were used to low-level format regularly with MFM drives so it was   
   >>> quite different when IDE came and the drives shouldn't be low-level   
   >>> formatted. :-)   
   >>>   
   >>> MFM drives needed to be "parked" before moving the drive (pc) using a   
   >>> small program. IDE drives do this automatically (moving heads outside   
   >>> the writable area).   
   >>>   
   >>   
   >> Some MFM drives require manual parking of the heads, and some do   
   >> auto-park. In particular, I have an old 40 meg drive from a PC that uses   
   >> the spin-down energy to generate power to auto-park the heads.   
   >>   
   >   
   > I will stretch to "Most MFM drives require manual parking..." and here   
   > better safe than sorry is a good idea.   
   >   
   > Actually parking is only required if you need to move the drive, or the   
   > pc it is in.   
   >   
   > What brand is it? I think I also have seen such a beast, but it was not   
   > common, probably expensive. I think it was in the era when IDE, SCSI,   
   > MFM and RLE drives coexisted.   
   >   
   > I always park MFM drives before turning off a machine and I have several   
   > (Olivetti M24, HP Vectra QS/20 etc. not used very often use though).   
   > Most of my MFM drives are 20MB. Some are really slow to spin up but they   
   > still work nicely.   
   >   
      
   ISTR that the auto-parking MFM drive I had was a Seagate 251-N.   
      
      
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   |     Charles and Francis Richmond       |   
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