I have a bunch of .dsk RT11 400k image files I need to write to
RX50 disks so I can boot from them on my 11/73
such as:
PBM 1000
Tandy 2000
Eagle II
Toshiba T300
Altos
Canon AS100
IBM PC/JX
Seiko 8610
Televideo TS1603
or IBM PC/AT (5170) with 1.2M
On Thu, 14 Sep 2017, Warner Losh wrote:
None of those system produces disks that are quite right... They may work
for short-term transfers, but long term the data retention rates are
terrible.
All of THOSE, with the exception of the IBM PC/AT (5170) with 1.2M drive,
have hardware that is completely compatible with Dec Rainbow 100.
Those are all 96tpi, but NOT "high density/1.2M".
They have capacities ranging from 640K to 800K, often
rounded/over-simplified to call them "720K" or "quad" density.
ALL, of course, require appropriate software, since RX50 is not the
"native" format for the operating system on them.
On the IBM PC/AT (5170) with 1.2M, admittedly the only one that is
easily readily available, there is trivial software tweaking
required to format/write "720K"/"quad" density, instead of "high" density:
300 bps with single speed (360RPM) drive; 300 RPM/low density for dual
speed drive.
Admittedly, none of the Dec Rainbow 100 diskettes that I wrote with PC/AT
are more than 30 years old. Yet.
There is no hardware incompatability that would cause data retention
problems if you are using the correct diskettes, written at the correct
data transfer rate for the rotational speed.
If you are having data retention problems, then it could be due to trying
to use HD ("1.2M"/600 Oersted) diskettes, when you need 300 Oersted
("360K/720K") diskettes.
HD/600Oersted diskettes recorded at "double" density (such as
"360K"/"720K"), instead of "high" density ("1.2M") will lose their
content very quickly. The color of the cookie is slightly different;
presence or absence of hub-ring is not a reliable indicator of which type
of diskette.
(Dec Rainbow is SSDD 96tpi, with similar disk format (not necessarily
circuitry) to MOST of the "quad" density systems, other than only using
one side. Similar to "720K" formats, but with 10 512 byte sectors per
track, instead of 8 or 9.)
--
Grumpy Ol' Fred ci...@xenosoft.com
