[Coco] Strange.... two 40 track disks on one 80 track disk?

[Fedor Steeman]

Hi Tim,

Oh, that would be great. If we exchange snail mail adresses, I could send
you a batch of floppies for you to experiment with.

The main aim for me is saving the content of this huge amount of diskettes.
Once the contents are safely copied onto a modern computer's hard drive, I
would probably toss most diskettes out.

Cheers,
Fedor


2009/11/1 Tim Fadden <t.fadden at cox.net>

> Fedor,
>
> I do have a 80trk 5-1/2 inch drive in one coco3 system if you would like me
> to give it a shot.
>
> Tim Fadden
>
>
> Fedor Steeman wrote:
>
>> Hi all,
>>
>> Thanks for all the responses.
>>
>> I am quite sure these disks are single-sided and that they came from a
>> setup
>> that could use and access 80 track disks. The collection of stuff
>> (including
>> the diskettes) I inherited is quite extensive and were used by a highly
>> skilled CoCo user. There are drives that are cleared marked as switchable
>> to
>> 80 tracks, there are diskettes clearly marked as being 80 tracks. Heck,
>> there are even disk controllers with a 40/80 tracks switch (?). I tried
>> those but that did not work either.
>>
>> I am quite sure there was some trick applied when he backed up the
>> diskettes
>> two at a time, but I would not know what. As suggested, I will try looking
>> through the stuff to see if there was any hardware or software involved. I
>> will also think about all the interesting suggestions you guys made so
>> far.
>>
>> Most of the diskettes are RSDOS BTW.
>>
>> /Fedor
>>
>> 2009/11/1 Arthur Flexser <flexser at fiu.edu>
>>
>>
>>
>>> Of course, if his drives are single-sided, no amount of poking will let
>>> him
>>> access the back!
>>>
>>> Art
>>> On Sat, Oct 31, 2009 at 8:25 PM, Christopher Hawks <chawks at dls.net>
>>> wrote:
>>>
>>>
>>>
>>>> Fedor Steeman said the following on 10/31/2009 03:50 PM:
>>>>
>>>> Hi,
>>>>
>>>>
>>>>> Some time ago I acquired this huge collection of diskettes that were
>>>>>
>>>>>
>>>> part
>>>
>>>
>>>> of
>>>>> a user group's CoCo software library. A lot of these are backups of
>>>>> backups
>>>>> so there is bound to be a lot of stuff I will be able to recover.
>>>>>
>>>>> There are a large number of diskettes that seem to contain a backup of
>>>>>
>>>>>
>>>> two
>>>
>>>
>>>> 40 tracks diskettes on one side of an assumed 80 track diskette.
>>>>>
>>>>> However, I can only access the first diskette of each of these backup
>>>>> floppies. I know because some of them have their contents listed on the
>>>>> envelope (or whatever you called the paper bag the diskette is in).
>>>>>
>>>>> I have a drive that can be switched from 80 to 40 tracks but that made
>>>>>
>>>>>
>>>> no
>>>
>>>
>>>> difference.
>>>>>
>>>>> Is there some way in HDB DOS that I am using (or RSDOS for that matter)
>>>>> that
>>>>> would enable access to the other 40 tracks and thus the other diskette
>>>>> backup?
>>>>>
>>>>>
>>>>>
>>>> Fedor:
>>>>
>>>>       It may be that the other tracks are on the other side of the disk
>>>> (not as in a flippy).
>>>>
>>>>       On a Coco 3 (or a 1 or 2 in ram) with DECB 2.1 (1.1), POKE &HD89F,
>>>> &H40 will make drive 2 the backside of drive 0. Likewise POKE
>>>> &HD8A0,&H41
>>>> will make drive 3 the back of drive 1. There a 4 memory locations that
>>>>
>>>>
>>> are
>>>
>>>
>>>> the drive mask (&HD89D - &HD8A0) the relevant bits are:
>>>> bit 0 - drive select 0 (&H01)
>>>> bit 1 - drive select 1 (&H02)
>>>> bit 2 - drive select 2 (&H04)
>>>> bit 7 - side select    (&H40)
>>>>
>>>>       These can be manipulated to access any side of any (physical)
>>>>
>>>>
>>> drive
>>>
>>>
>>>> as any drive number.
>>>>
>>>> --
>>>> Christopher R. Hawks
>>>> HAWKSoft
>>>> ---------------------------------------------------------
>>>> Never meddle in the affairs of NT. It is slow to boot and quick to
>>>> crash.
>>>>       -- Stephen Harris
>>>>
>>>>
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>>>>
>>>>
>>>>
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>>>
>>
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