[Coco] 3.5 in 720K vs 1.4 meg floppy diskettes

[Robert Gault]

Gene Heskett wrote:

> On Friday 12 December 2003 21:07, KnudsenMJ at aol.com wrote:
> 
>>In a message dated 12/10/03 11:08:11 PM Eastern Standard Time,
>>
>>bugster at cedarcomm.com writes:
>>
>>>1.44MB 3.5" Floppy drive acting as a 720k drive.....works great! 
>>>I've put together several dual floppy drives with this
>>>configuration and it works great with DD 720k floppy disks.  My
>>>current config at home is this configuration (/DO is a 360k 5.25"
>>>floppy and /D1 is a 1.44MB Floppy).
>>
>>Have
>>
>>
>>> yet to have a DD 720k disk fail on me (even formatted as 160k in
>>>RS-DOS!).
>>
>>This makes sense, since the drive electronics sense whether it's a
>>DD or HD diskette in there and adjusts the write current
>>accordingly.  But keep reading ...
>>
>>
>>> Putting a 1.44MB floppy disk in and formatting it as double or
>>>single density (720k or 160k under RSDOS)....sucks!  Very
>>>unreliable.
>>
>>Hmmm, sounds like the drive fails to upgrade the write current for
>>the HD floppy.  Maybe the OS has to help out in this, since you
>>seem to get better results under OS-9 than BASIC.  Or did I miss
>>something?  --Mike K.
> 
> 
> I think its related Mike.  I have 3 3.5"drives here, all recent 
> purchases, and they refuse to do a 720kbyte format on an HD diskette.  
> I've come to the conclusion that they self adjust the data recovery 
> pll for a 500 khz data rate when they sense the HD hole, and 
> therefore cannot deal with a 250 kilobaud data rate even during the 
> write phase, usually error out of that within the first 2-3 tracks.
> 
> Taping up the hole results in a format that doesn't quit during the 
> write phase, but has a very poor performance during the verify phase, 
> often marking a major portion of the disk out as unusable.  Put a 
> regular DD diskette in, and everything is cool.  I have several 
> hundred of those from my amiga days so I'm set for a while.
> 
> Currently I've a major problem.  The boot is failing because I rebuilt 
> one of my utility packs thats loaded during the boot by the startup 
> script.  Unforch, when I did the re-merge using merge, I then forgot 
> to set the x and px attributes, so when the startup script gets to 
> that line it outputs an error 214, followed by a 221 and hangs the 
> boot.  No response to anything but the reset button at that point.  
> Is there any way to cause it to bypass the startup and drop directly 
> to a shell, thereby allowing me to fix it?
> 
I don't remember anything like a key press that will bypass the Startup 
file. However, brute force could be used here.

Use a raw disk editor either from a good OS-9 boot or Disk Basic to 
change the name of the Startup file on the corrupted disk; S to X for 
example. Then when OS-9 starts, it won't find a Startup file.