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

[js at cimmeri.com]

On 2/22/2022 6:42 PM, Warner Losh wrote:
>
> On Tue, Feb 22, 2022 at 4:36 PM js--- 
> via cctalk <cctalk at classiccmp.org 
> <mailto:cctalk at classiccmp.org>> wrote:
>
>
>     Rod,
>
>        Not sure an RX33 (if 1.2MB
>     equivalent) would write working RX50
>     800k (double density) disks.  Very
>     different drives.
>
>
> The RX-33 is the same sort of drive 
> that you had in your PC if you wrote
> RX-50s with your PC. Back in the day, 
> lots of people used RX50.SYS to
> have it setup the transfer rates, RPM 
> and sectors per track parameters
> so that you could read/write them on a 
> PC running DOS. The parameters
> are basically the same ones you need 
> to write the 360k DOS floppies, only
> with twice the number of tracks and 10 
> sectors per track instead of 9 (this is
> done by making the track gaps smaller 
> and eeking an extra sector out of the
> deal, but using at the same data rates).

Thanks for reminding me, Warner.  To recap:

The format used on a RX50 disk is:
Single Sided, 80 tracks, 10 sectors per 
track
96 TPI, 300 RPM, 250 KHz data rate
... which translates to 400K SSQD.

The format of a high density 5.25" PC 
disk is:
Double Sided, 80 tracks, 15 sectors per 
track
96 TPI, 360 RPM, 500 KHz data rate
... which translates to 1.2MB DSHD.

So to use an actual RX-50 on my PC, I 
just had to use an FDC capable of 
slowing down the data rate, and make a 
floppy cable to route the signals 
properly (minor changes from a PC floppy 
cable).

What Rod *might be* running up against 
with using PUTR and his RX-33, is that 
his RX-33 RPM and data rate might not be 
slowing down to equal that of the 
RX-50... which could be an FDC problem. 
    Does the RX-33 automatically slow 
the RPM if the data rate drops to 250khz?

- John Singleton



>        I've successfully put an actual
>     RX-50
>     drive on my PC, and written RX-50
>     images
>     using PUTR.  You might try that route.
>
>
> Did you have difficulties with Pin34 
> not being the change disk pin? That's what
> I ran into when I tried this many many 
> years ago...
>
> Warner