[Coco] Floppy drive/OS9 issue

[Joel Ewy]

Hey Andrew,
  
  If your original Tandy drive is like mine, I suspect it is actually a  double-sided drive.  I'm sure others will correct me if I'm wrong,  but I believe that the very first CoCo disk drives -- the full-height  ones that were one-to-an-enclosure were single-sided, 35 track drives,  and all the other ones (including all the half-height ones) after that  were 40t, ds.  Disk BASIC was never updated to make use of the  extra capacity.
  
  As for OS-9, by default the device descriptors (d0, d1, etc) are  configured for 35t, ss.  So even though the drives are  double-sided, the device descriptor, which tells OS-9 what kind of  drive it is, says it's 35t, ss.  In order to read double-sided  disks, you need to use the dmode utility to change the descriptors to  40t, ds.  I think the command line to change /d1 would look  something like this:  "dmode /d1 cyl=28 sid=2"  Once done,  the descriptor can read 40t, ds disks, and can still read single sided  disks, IIRC.
  
  Now, I don't think dmode comes with the stock Tandy OS-9 disks.   You will need to download it somewhere and use a utility from one of  the emulators to put it on a CoCo disk.  At first glance I don't  see it on rtsi.com.  It may come with NitrOS9, I don't  recall.  If you have difficulty finding it, I or somebody else on  this list can probably send you a copy.
  
  On second thought, it's entirely likely that the original OS-9 System  Master disk comes with 40t, ds device descriptors.  On third  thought, in order to use them, you'd need to make a new bootfile with  OS9Gen (or something like EZGen), specifying them instead of the ones  you are using.  If you try to load a 40t, ds copy of /d1 when  there is already a single sided /d1 in memory, it ain't gonna  work.  And you can't unload the existing /d1 descriptor if it was  loaded up from the bootfile.
  
  But if you can locate dmode and get it on an OS-9 disk, that would  definitely be your easiest route.  To make the change permanent,  you will need to make a new bootfile.  But this should be easier  because you can just use cobbler, which is much more straightforward  than OS9Gen.

  As for the IDC connectors, I haven't checked recently, as I still have  a small stock, but I would be surprised if you couldn't still get them  somewhere.  If you do make your own cable, just don't use a PC  floppy cable as a reference.  The connectors are the same, but the  CoCo uses floppy drives as they were originally intended and actually  makes use of the drive select lines and jumpers.  The reason your  second drive is set to drive 1 is that it has probably been in a PC,  where all drives are jumpered to drive 1, and drive selection is done  with an ugly twist in the ribbon cable.  On the CoCo it's a  straight-through cable.
  
  If you can't locate a new floppy connector, you can carefully remove  one from an old PC floppy cable and, if you don't break it or munge the  pins in the process, re-crimp it onto a CoCo cable.
  
  Good luck!
  
  JCE
  
Andrew <keeper63 at cox.net> wrote:  All,

As some of you may or may not know, I am involved in a project to help 
convert some 400+ disks over to emulator formats. Normally this wouldn't 
be a problem, but in these early stages I have found something out that 
I didn't know before, and I am wondering if there is a solution of some 
sort.

I am at a point in the project where I am verifying/checking-out a bunch 
of OS-9 floppies. My main problem is that some of these disks are two 
sided, and OS-9 L2 is complaining when I stick them in my drive, with an 
error #249 "Wrong Type", which according to the manual may mean they are 
double sided (one of the floppies was marked as double sided, so I am 
assuming for now this is the problem). Other OS-9 floppies read OK.

Let me give you a little background on my drive situation, though. When 
I first had my Color Computer 2, I had a tape drive (this was about 1984 
or so, and I was about 11 years old). About a year later I was given a 
floppy drive by my parents. It was an FD501 system, with the single 
half-height drive in a dual drive cabinet. A few years later I upgraded 
to a Color Computer 3, and a little after that got a 512K expansion 
(third party, but I can't remember who, just not the RS one).

In high-school my drive controller died (still don't know why, and I 
still have it). I managed to get from a friend an FD502 controller 
cartridge. My drive worked at that point.

About 10 years later I get all of my Color Computer stuff back from my 
parents house. I plan to do a conversion of my software to work on 
emulation. I try my drive, and it won't read anything. I purchase a 
drive off of a guy on ebay to replace the one I had. It works great, and 
I finish my conversion project.

I was never an OS-9 fanatic, but I now want to get to know it better, 
since I didn't when I was younger, and I kinda need to for this floppy 
conversion project.

So, here I am trying to go thru these floppies last night, and I am 
running into two issues - sometimes I need a command module which isn't 
loaded, so with a single sided system I am needing to swap floppies, and 
the other issue is that I have floppies that are double sided. I figure 
"hey, bright idea - I have another 5.25 drive in my shop (don't we 
all?), maybe it is double sided?" - thinking I will add the drive, and 
all will be well.

I pull the drive out, and it is double sided - but it won't hook up to 
my system! Basically, it will plug in, but I can't use both drives 
because of the way the connector is configured and the cable connectors 
in the case - the one drive in the case has the connector on one side 
facing in one direction, and this other drive (by a different 
manufacturer) has it on the other side oriented differently - and the 
cable that goes in has the connectors space about an inch apart, can't 
twist them much, etc. Drats!

Well - I figure I will just plug the new one in, and it will at least 
give me a double-sided drive, fixing one of my issues, hopefully. I try 
it out, and it doesn't quite work right - If I issue a DIR 0 (or just 
DIR) no action. But issuing a DIR 1 works OK. I take another look at the 
drive, and sure enough, there are a set of jumpers marked D0, D1, D2, 
and D3 - and the jumper is on D1 (interestingly, there is another set of 
jumpers labeled U0, U1, and U2 - the drive is a TEAC FD-55BR). I assume 
(though I have yet to try it), that if I pop it over to D0, it might 
work OK (?). But what about my other drive (the one I have been using 
for the past few years)? Does it have jumpers?

I look at the drive closely, and I don't see any, but it has a cover 
obscuring the drive electronics. The cover looks like it is meant to be 
removeable, so I remove it carefully. What I see shocks me a little bit:

...An upper drive head!

All this time - the drive has been a double sided drive! But it doesn't 
seem to work as a double-sided drive! It only sees a single side. I also 
don't see any obvious jumpers. It is a CHINON FZ-502.

So - after all this, 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

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