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

[Gene Heskett]

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?

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.22% setiathome rank, not too shabby for a WV hillbilly
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by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.