[Coco] Regarding disk drives

Sat Jan 3 09:42:07 EST 2009

Hi John,
If you ever get Eagle figured out please let me know! BTW, I would be 
interested in any circuits you have for the CoCo or CoCo related projects.
Have a nice day.

Alan Jones

-- 
N8WQ - Canal Winchester, Ohio
http://exwn8jef.googlepages.com/home
http://n8wq.blogspot.com

John Eric wrote:
> Yes, I remembered reading that the CoCo used the side select signal as the drive3 (4th drive) select. The IBM cables I have (actually 3M) are the same as the old IBM cables with the exception of an added connector intended for a tape drive, but which is actually just another 5.25" type edge connector. Looking at these cables, I could probably snip the two end connectors (after the twist) off and use the one intended for a tape drive and the one intended for ibm drive b for the coco drives, then I would only need to replace the header connector with an edge connector to connect to the coco fdc. I do have a homemade fdc that I made from a TMS2793 and i allowed for either edgecard or header type connection to the controller when I built it. It was a pain getting it to work (getting the two variable resistors set properly - finally had to buy an oscilloscope, or maybe that was just an excuse because I wanted a scope :) I really didn't design it - I based it
>  on a schematic of a Dragon controller  I found last year - only 10 I.C.'s counting the eprom and smaller than the fd-502. I had to get a friend to layout and make the pcb - I'm no good at that - he has since moved away, thus I am trying to learn EAGLE. If I can just find what i did with the schematic, I could upload it. The original schematic used a 2797 but I was able to get it to work with a 2793. Jeric
>
>
>
>
> ________________________________
> From: Bill Barnes <da3m0n_slay3r at yahoo.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Saturday, January 3, 2009 1:10:15 AM
> Subject: Re: [Coco] Regarding disk drives
>
> Forgot to mention, as in the IBM case, you can only use two drives with the IBM cabling.  The way the CoCo signals are, can only use three  drives in DSDD mode.
>
> -Later!   -WB-    -- BABIC Computer Consulting.
>
>
> --- On Sat, 1/3/09, John Eric <jet.pack at ymail.com> wrote:
>
>   
>> From: John Eric <jet.pack at ymail.com>
>> Subject: Re: [Coco] Regarding disk drives
>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>> Date: Saturday, January 3, 2009, 12:06 AM
>> I wasn't too clear at the end of this. What I was
>> meaning is if I jumper two drives as drive 1 and connect
>> them to the IBM cables drive a and drive b connectors, that
>> should give me drive 0 and 1 on coco and if I jumper a 3rd
>> drive as drive 2 and connect it to the connector intended
>> for a tape drive, that should work as coco drive 2. I'm
>> going to go ahead and order the idc crimp tool as I realize
>> it will have many uses, such as making a CM-8 extender
>> cable, etc.
>>
>> jeric
>>
>>
>> ________________________________
>> From: John Eric <jet.pack at ymail.com>
>> To: CoCoList for Color Computer Enthusiasts
>> <coco at maltedmedia.com>
>> Sent: Friday, January 2, 2009 11:53:14 PM
>> Subject: [Coco] Regarding disk drives
>>
>> I decided to upgrade two of my CoCo's floppy diskette
>> drives to DSDD 360K units.
>> After installing drives 0 and one, setting the appropriate
>> jumpers and making sure only the second drive had the
>> terminator resistor pack, I was ready to go... or so I
>> thought.
>>
>> One of the units, both drives worked fine, as DSDD.
>> The other unit, one of the drives couldn't read squat.
>>
>> Although both appeared to be Tandy's cabling,
>> apparently one of the cables differed. A quick look -
>> Tandy's nonsense of pulling pins to select the drive. I
>> had forgotten about that. Looking at the original drives,
>> drive 0 had both the 0 and 1 select jumpers soldered right
>> in, and the second drive had only the drive 1 jumper. In
>> fact, all of my Tandy drives were like this.
>>
>> Simple solution, crimp new connectors on a cable. However,
>> I just had a thought. If I were to use IBM type floppy
>> cables and jumper both drives as drive 1, that should work,
>> right? I ask because I have a box full of 3M IBM type floppy
>> + Tape drive cables - they have the standard 4 connectors at
>> the end - 3.5" and 5,25" for Drive A (IBMspeak)
>> and the same for drive B, separated by about 6" of
>> cable, and then about 6" later, another 5.25" type
>> connector intended for a tape drive. So, my thinking is, if
>> I jumper two drives as drive 1, the end connectors will
>> access them as drive 0 and 1 (because of the twist in the
>> cable), and if I jumper a third drive as drive 2, the third
>> connector should acces it as the third CoCo drive. So,
>> before I order the IDC cable crimper and some connectors
>> (the end that hooks to the FDC will have to be replaced with
>> a CoCo type connector) - does this sound right?
>>
>> Thanks - JEric
>>
>>
>>
>>      
>>
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