[Coco] Good news: my CoCo 3 is back to life!

[Joel Ewy]

Mark Marlette wrote:
> Joel,
>
> MB8877A was a 5v drop in replacement for the +12v WD1793, otherwise
> you would need a MPI for that device.
>
> SY6591...that is it...No datasheet on that one at Cloud-9's
> repositiory... :(
>
> I knows there was a mod for the J&M to work on the CC3.
>
> Mark
>
    Well, the one I have I got second hand (in fact, it came to me in a
hacked-up standard full-length black plastic drive controller case with
a Hard Drive Specialist sticker which was about 1/3 torn off so somebody
could get to the screw.  So it's possible that it was modified before it
got to me.  But if so, it was a _very_ subtle modification, as I see no
jumper wires soldered on anywhere, and all the solder joints on the back
side look original.

And just this morning I checked it out on a CoCo 3.  I used it to load
up a saved Sockmaster hi-color picture, and it worked like a charm. 
Maybe the modification was for 2MHz operation.  I didn't check that out.

As for a data sheet, I think the SY6591 may be a second source of the
WD-1791.  I bet James Daggett could confirm or refute that...

JCE
> Quoting Joel Ewy <jcewy at swbell.net>:
>
>> L. Curtis Boyle wrote:
>>> On Mon, 05 Mar 2007 08:31:49 -0600, Boisy Pitre <boisy at boisypitre.com>
>>> wrote:
>>>
>>>> Gents,
>>>>
>>>> Not to put too fine a point on it, but FD-500 controllers will also
>>>> work at 5v.  I think it's a very older, specific model number of disk
>>>> controller that requires 12v and hence, the MPI.
>>>>
>>>> Boisy
>>>>
>>>
>>> The very old, full size controllers that came with original full
>>> height, really long grey 35 track single sided drives were the 12V
>>> controllers.
>> FWIW, I have a 26-3029, a 26-3129, a J&M (says JFD-COCO rev.A on the
>> PCB), a Disto Super Controller, and a couple Super Controller IIs.  They
>> all work on the CoCo 3 without an MPI.  (And none of them are an FD-501
>> :) )  My 3029 has an MB8877 FDC with a WD9216 data separator.  The
>> controller in the J&M is an SY6591.  All the rest use the 28-pin WD1773.
>>
>> Mike Pepe notes in an email on this list on 8/2/06 that the original
>> controller (the one that required 12V on the bus) was the 26-3022.  So
>> that should be the only one you would need to plug into the MPI to use
>> with the CoCo 3.
>>> Ironically, the only ones that could properly handle hi-density (1.2
>>> or 1.44 MB) drives with some modifications to the controller.
>>>
>> This fall Mike Pepe modified his  3029 for high-density and posted a few
>> messages about it on this list.  Last I recall he still needed to
>> finalize the software/firmware modifications.  His notes are here:
>> http://www.doki-doki.net/~lamune/computers/coco/hd-floppy/
>>
>> JCE
>>>
>>> --L. Curtis Boyle
>>>
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>>>
>>
>>
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