[Coco] Floppy drive/OS9 issue

[Joel Ewy]

Gene  mentions 80t 5.25" drives, and that they may need to be modified to use  with a CoCo controller.  3.5" 720K and even 1.44M floppy drives  work with an ordinary CoCo disk controller without modification.   The 1.44M drives only work at 720K capacity.  I've switched  entirely to 3.5" disks on my CoCos.  There's quiet a bit of wasted  capacity in RS-DOS, but if you have a DOS patched for double-sided  operation, you can at least use the back side.  In OS-9 you can  use the full 720K.  
  
  (How hard would it be to patch DECB to add a constant value (say 40) to  the track number?  That way you could have drive 0, 1, 2, 3, be  the first 35 tracks of drive 0, side 0; drive 0, side 1; drive 1 side  0; drive 1, side 1; and drives 4, 5, 6, 7, be the corresponding  drive/side but from tracks 40-75?  That way you could squeeze the  contents of 4 CoCo disks on a single 720K floppy.)
  
  The 3.5" drives are probably more plentiful these days than the old  5.25" drives, and the media aren't as ancient.  One potential  problem with using 3.5" drives on the CoCo:  few of the more  recent drives have a drive select switch or jumper anymore.   They're hardwired to drive 1, because PCs have long since forgotten  that you can use more than 1 floppy, let alone 3 on the same  cable.  So if you have an old '386 lying around (and who doesn't  have about 8 or 10 of them?) you might see if you can scrounge a floppy  drive from it that still has a way to select a drive number other than  1.  Alternately you might hunt around on the circuit board to see  if there are solder pads for jumpers you can wire in.
  
  JCE
  
  Gene Heskett <gene.heskett at verizon.net> wrote:
  
  >On Saturday 22 July 2006 15:12, Andrew wrote:
  >>All,
  >>
  >>... my question to all of you guys is: what do I do?
  >>I have the folowing drives:
  >>
  >> CHINON FZ-502 (acts as a single sided drive, but is double)
  >>         TEAC FD-55BR (works as a single sided drive, but may jumper
  >> to double)
  >>
  >>Personally, I would like to have them both working, and have two
  >> double sided drives in my system (at some point in the future, when
  >> cloud-9 gets going again, I plan on getting a hard drive controller).
  >> It would make my OS-9 world much easier to work in, and would make
  >> this conversion much easier.
  >>
  >>Does anyone have any ideas on this - does anyone have any information
  >> on either of these drives or how I can/should set them up? Also, can
  >> I still buy the connectors that are on my cable to crimp my own
  >> custom cable so I can hook these drive up - what kind of connector is
  >> it (can I order it from DIGIKEY or someplace)?
  >>
  >>Any information posted will be appreciated! Thank you,
  >>
  >>-- Andrew L. Ayers
  >>    Glendale (Phoenix), Arizona
  >
  >What you want is to pitch the missing teeth drive connectors in the 
  >trash, and replace them with connectors that have all the connections 
  >present.  One could at one time, purchase those connectors at the shack 
  >but they've been stripping the parts cabinet pretty badly of late so 
  >you may have to shop around or hit the catalogs.  You'll best use a 
  >small vise to install them properly, although I have used a hammer and 
  >or vise-grips.  The vise doesn't leave as many marks on the 
  >cosmetics. :)  You can re-space the connectors to make room for the 
  >twist required while you're working on the cable.Once thats done,  then put both >drives in, one set as DS0 and one set as DS1. Make  sure the terminating >resistors are only present in the drive thats  last on the cable. They'll probably be
  >in a dip socket near the DSx jumpers.
  >
  >Having established that, then the rest of it will be more or less self 
  >explanatory by looking up the docs on the dmode command.  And there are 
  >2 versions of that extant that I know about, with slightly different 
  >syntax requirements, but I don't have the edition numbers of the two of 
  >them commited to non-volatile wet ram.
  >
  >There are also a lot of 80 track drives about, some rated at 720k,  some at >1.2megs capacity. Only the 720k can be used on the coco's  without extensive >mods to the controller, and it has to be the  original, needs 12 volts to run tandy >version. The 1.2 meg drives  can be used at 720k IF you can find the motor
  >speed jumper and slow it down from 360 rpm to 300 rpm.With the  right floppy >driver and the right descriptor settings via the dmode  command, 40 track disks >can be read, but not written to, in the 80  track drives. Writing to such a disk >only writes a narrow piece of  the 40 trackers wider track, and generally trashes >the disk until  its reformatted in the proper drive.
  >
  >-- Cheers, Gene
  >...