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

[Tim Fadden]

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
>>>
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>>>
>>>       
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>>
>>     
>
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