[Coco] Strange.... two 40 track disks on one 80 track disk?
petrander at gmail.com
Sun Nov 1 15:02:38 EST 2009
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.
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!
> 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
> >> 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
> >> 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
> >> 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
> > 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)
> > 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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