22 Feb
2022
22 Feb
'22
4:08 p.m.
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