[Coco] Cable assistance

[gene heskett]

On Saturday, February 19, 2011 08:14:52 am Richard Ivey did opine:

> I am wanting to modify my dual disc drive enclosure.  I want it to have
> a regular 5.25 disc and a 3.5 inch floppy.  I want it set up where the
> 3.5 is the primary.
> 
> I am willing to pay you for supplies AND labor, or I can collect the
> cables and whatnot and send them to you.
> 
> Thanks Group.
> 
This is not as easily done when the requirement is for the 3.5 inch drive 
to be drive 0.  This essentially means that one must cobble up his drive 
cable from a 'twisted' pc cable, which unless you've a well stocked junkbox 
of old pc cables laying around, is getting more difficult.  If you have 
such a cable, then installing the 34 pin card edge connector usually will 
fix it right up.

The reason being that the 3.5" drives made for the last 25 years are all 
programmed to be drive 1.  So unless you can do some trace cuts and 
jumpering on the 3.5" drive in order to assign its address as drive 0, the 
twisted cable will be required.

Secondarily, and I have at least 2 such drives myself, is that the data 
recovery circuits in many of the later drives cannot operate at the coco's 
250 kilobaud rates, aka the DD, not HD data rates.  That seems to be 
married to the HD hole in the diskette case.  But covering the hole also 
turns down the recording currents, usually so far that a decent, long 
lasting recording cannot be made.  I have played with this a bit, and have 
found in a case or two where I could format the disk, and make a boot disk 
that faded within an hour to an unbootable disk.

Because dealing with a 3.5" as drive 0 is such a pima, I have relegated 
their use to only drive 1 here.

Even that is of relatively little utility since I built this machine 
several years ago, as this $300 ASUS motherboard has an FDC that cannot 
deal with 256 byte sector disk formats regardless of what I tell it with 
setfdparm. (linux of course), so while I can pull the latest cvs image for 
nitros9 and rebuild it locally using toolshed, I have resorted to using sz 
to send that built image to the coco over a 9600 baud serial cable, then 
copy it to a small clean scsi hard drive and adjust the /S1 drive with 
dmode to make it think that hard drive is an 80 track floppy, at which 
point it is entirely usable just as if it was a floppy, but 10x faster.  
With a TC^3 controller, I can now have all 3 scsi hard drives available but 
haven't actually done it yet as I need to rebuild my drive tower to hold 
the 3 floppies and the 3 HD's plus a cdrom, and its out of room. :-[

I'm also playing with drivewire 4, but haven't worked out how to fit that 
into the available 'system' ram, so I can't just mount that built image 
directly. Yet.  I do have a printer working over drivewire 4 though, neat!

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
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The difficult we do today; the impossible takes a little longer.