Installing an operating system on the 11/83 - update.

[Warner Losh]

On Tue, Feb 22, 2022, 8:43 PM Jay Jaeger via cctalk <cctalk at classiccmp.org>
wrote:

> On 2/22/2022 6:12 PM, js--- via cctalk wrote:
> >
> > On 2/22/2022 7:00 PM, Ray Jewhurst wrote:
> >> I read that you can indeed use a standard 1.2 Meg drive and that you
> >> can also use DSHD 5.25 disks in place of RX50s. Is there any truth in
> >> this? If there is it will be much easier and cheaper to make disks for
> >> my Rainbow.
> >
> >
> > As Chuck noted, I'd think you'd want to use 360K media -- not DSHD
> > diskettes... and ensure that the 1.2MB drive is slowing down to 300RPM
> > with a data rate of 250KHZ.
> >
> > These features will depend on the 1.2MB drive you have, as well as your
> > FDC and imaging software.
> >
> > - John Singleton
>
> Writing a 360KB or RX50 diskette with a 1.2MB drive is a path to a lot
> of frustration.  Not only do you have to double step the drive (software
> often takes care of that part), but the tracks written will be narrower
> than a real RX50 / 306KB drive, providing a smaller signal/noise ratio.


Not true. Not for RX50 at least. Both the 1.2MB format and the RX50 format
use 80 tracks. There is no double stepping or half width tracks involved.


>   And, if you don't start with completely magnetically erased media, any
> left over junk in any data left over may be picked up by the RX50 head.
>

Also not true. Writing a full track to format it results in well formed
media. As long as you don't use HD media. DD or QD media works just fine.

Been there, done that.
>

I have as well, and things don't work the way you say. The TEAC 55 drives
are able to do this. In college I exchanged data between a data collection
AT and a MicroVAX ii on RX50 media. It was sometimes formatted on my
Rainbow at home and later on the AT since I got tired of being in the loop.
We had none of these problems as long as we avoided HD media.

Warner


> JRJ
>