[Coco] CoCo floppy disk subsystem

Arthur Flexser flexser at fiu.edu
Thu Jan 14 14:21:31 EST 2021


Note that it says on p1 of the spec sheet, "Upward compatible with Western
Digital FD1793-02".  (Not sure what the -02 suffix indicates.)

Art



On Thu, Jan 14, 2021 at 2:10 PM Arthur Flexser <flexser at fiu.edu> wrote:

> P.S.  The full designation of the chip I'm talking about is MB8877A.  Spec
> sheet is here:
>
> https://www.digchip.com/datasheets/parts/datasheet/170/MB8877A-pdf.php
>
> It appears to be available for under $10--a lot cheaper than a multipak,
> if using a 26-3022 with a CoCo 2 or 3 is the only reason you need a
> multipak.
>
> Art
>
> On Thu, Jan 14, 2021 at 1:48 PM Arthur Flexser <flexser at fiu.edu> wrote:
>
>> I seem to recall using my 26-3022 controller with a CoCo 2 without a
>> multipak.  The reason this worked was presumably that I had had to replace
>> the WD1793 controller chip some time previously, and the replacement sent
>> to me was a Fujitsu 8877, which I believe doesn't require 12V.
>>
>> Can anyone confirm this about the Fujitsu chip?
>>
>> Art
>>
>> On Thu, Jan 14, 2021 at 1:30 PM John Mautz <ejmautz2 at gmail.com> wrote:
>>
>>> According to cocopedia.com the 26-3022 is not compatible with the CoCo2
>>> or
>>> 3 without using a Multi-Pack.
>>>
>>> http://www.cocopedia.com/wiki/index.php/26-3022
>>>
>>> The controller is based on the Western Digital WD1793. It features an
>>> analog data seperator circuit, infamous for its inherent unreliability
>>> and
>>> has multiple potentiometers which are used to calibrate various delay and
>>> timing features of the disk-side interface. It requires a +12 volt DC
>>> supply to operate, and is thus not compatible with a CoCo 2 or 3 unless a
>>> Multi-Pak Interface (or other source of +12V) is used or the CoCo or
>>> controller are "hacked", also contains the Disk BASIC ROM chip, and the
>>> necessary interface logic.
>>>
>>> Hope you have a multi-pack.
>>>
>>>
>>> On Thu, Jan 14, 2021 at 12:39 PM Salvador Garcia via Coco <
>>> coco at maltedmedia.com> wrote:
>>>
>>> > Happy New Year all. Thanks to Rietveld's exploration with using the
>>> GoTek
>>> > with a CoCo and other computers, I was motivated to get a GoTek myself
>>> to
>>> > test my floppy drive subsystem that is not working correctly.
>>> >
>>> > I have the 26-3022 floppy drive and controller. I had this working
>>> back in
>>> > the 80s with my CoCo 1. This past December I decided to unpack it all
>>> and
>>> > give it a run. Much to my dismay, the floppy drive subsystem did not
>>> work
>>> > as expected. I got as far as getting the formatting process started
>>> with
>>> > DSKINI 1, but after the head steps 34 times and seeks, I would get the
>>> > dreaded IO ERROR.
>>> >
>>> > Since I was on vacation in Mexico, I decided to bring back with me the
>>> > 26-3022 controller (the drive was too cumbersome and heavy).
>>> >
>>> > My plan is to swap out parts, specifically, the drive and cable, hoping
>>> > that the problem is with one of these. I have no way to swap out the
>>> cart
>>> > controller. I got the GoTek to substitute the floppy drive and I
>>> already
>>> > ordered and got a new 5.25" drive flat cable, with no twist.
>>> >
>>> > I received my GoTek yesterday and am in the process of installing the
>>> > FlashFloppy firmware. Here is what I have:
>>> >
>>> > 1. CoCo 2 and 3
>>> > 2. 26-3022 cart controller plus original flat cable
>>> > 3. New 34 pin flat cable for 5.25" floppy drives (this has one
>>> connector
>>> > at each end)
>>> > 4. 34-pin edge connector to IDC adapter (to connect the 5.25" drive
>>> cable
>>> > to the GoTek)
>>> > 5. GoTek emulator SFR1M44-U100K-R
>>> >
>>> > Am I able to build a working floppy disk subsystem using these items?
>>> Or
>>> > asked another way, is the 26-3022 compatible with the CoCo 2 or 3?
>>> >
>>> > Any tips or advice on building this system?
>>> >
>>> > As always thank you all for your time and assistance. Salvador
>>> >
>>> > --
>>> > Coco mailing list
>>> > Coco at maltedmedia.com
>>> > https://pairlist5.pair.net/mailman/listinfo/coco
>>> >
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> https://pairlist5.pair.net/mailman/listinfo/coco
>>>
>>


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