On Thu, Sep 14, 2017 at 4:05 PM, Fred Cisin <ci...@xenosoft.com> wrote:
> 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.
>
Right. I didn't see the Atari on the list, which was the only one, prior to
this thread, that I knew for sure had the right drives in it... I also
misread the IBM PC/JX as pcjr, which had the 360k floppy drive in it.
> 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.
>
You need hardware tweaks as well to make the drives compatible. Otherwise
the recording strength is too high.
> 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.
>
The problem is people try to write RX-50 media with the HD drives. The
difference in recording strength causes many of the retention issues. It
works better when you write with the IBM drive with HD media. This may
also be drive specific, as the different drive makers have had different
levels of competence with the old standards...
> 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.
>
True.
(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.)
>
Yes. I ran TEAC FDC55FRs in my Rainbow for years to get double-sided space
(with tweaks to DOS from a gentleman in New Mexico).
Warner
