17 Jan
2005
17 Jan
'05
2:19 p.m.
Hi Eric
I think he means that as long as he stays on that drive,
he has no issues. The write problem is obvious to anyone
that thinks about it a little ( I hope ).
1. A truely blank disk ( bulk erased ) can be formatted
and written on by a 1.2M drive and will work in most
cases on a 360K drive. This may written on by a 360K
drive as well and still work on a 360K.
2. Once a disk has been written on first by a 360K drive
and then a 1.2M, it can only be read on a 1.2M drive!
That's life.
Dwight
From: "Eric Smith" <eric(a)brouhaha.com>
Doc wrote:
I have a 5.25/3.5" combo drive that
handles all four of those formats
(and 3.5" 360K) just fine. The gorgeous part is that it occupies a
single 5.25" bay.
Won't write 360K 5.25" disks reliably. 1.2M drives have a narrower head
gap than 360K drives, because they use 96 TPI rather than 48 TPI.
Eric
17 Jan
17 Jan
2:56 p.m.
Dwight wrote:
2. Once a disk has been written on first by a 360K
drive
and then a 1.2M, it can only be read on a 1.2M drive!
Even that won't necessarily be reliable; if the head alignment
is even slightly off, by an amount that would not normally
cause problems with 1.2M disk interchange, it can cause problems
reading 360K disks that have been written on 1.2M drives.
Eric
5:04 p.m.
Dwight K. Elvey wrote:
Hi Eric
I think he means that as long as he stays on that drive,
he has no issues. The write problem is obvious to anyone
that thinks about it a little ( I hope ).
I don't just stay on that drive. If I did, I wouldn't need it in the
first place.
1. A truely blank disk ( bulk erased ) can be
formatted
and written on by a 1.2M drive and will work in most
cases on a 360K drive. This may written on by a 360K
drive as well and still work on a 360K.
2. Once a disk has been written on first by a 360K drive
and then a 1.2M, it can only be read on a 1.2M drive!
That's life.
No, that's wrong. At least, it's not necessarily true.
I have formatted disks for an RX50 on the 1.2MB drive, written data
to them on that drive, and used them on a PDP-11. I have also used
floppies to back up an RSX-11S disk on "real" RX50 disks, transcribed
that to PC, overwritten them on the PC without a low-level format, and
read them on the PDP-11. I have had some floppies fail, but they always
failed either on the RX50 drive *before* they were ever in the 1.2MB
drive, or they failed format on the 1.2MB drive before they ever made it
to the PDP-11.
I don't doubt the information I'm reading, that the track written by
the 1.2MB drive is narrower than the track written by a native 360K
drive. I'll even stipulate that my experience is limited to writing
disks for PDP-11s and the Altos 580 (DSQD I think; I haven't played with
that box in a long while), so I can't speak to the reliability on other
platforms.
I *can* say that in writing, overwriting, transcribing, and reading
RX50[0] floppies between a real PDP-11 and a Linux PC with a 1.2MB 5.25"
drive, track width has never been an issue. The few disk failures I've
had never got far enough to bring that into play.
Doc
[0] Both original NIB RX50-formatted 3M floppies, and 1.2MB DSHD
floppies formatted according to Pat Finnegan's fdformat/superformat
parameters.
5:28 p.m.
Doc Shipley declared on Monday 17 January 2005 11:04 pm:
Dwight K. Elvey wrote:
Umm, the RX50s and Altos 580 floppies you've used are 80-track (96tpi)
disks just like 1.2MB floppies. 360k floppies are 40-track (48tpi)
disks. So, they're the same track width as a 1.2MB disk, not a 360k
disk.
Pat
--
Purdue University ITAP/RCS --- http://www.itap.purdue.edu/rcs/
The Computer Refuge --- http://computer-refuge.org
1. A truely blank disk ( bulk erased ) can be
formatted
and written on by a 1.2M drive and will work in most
cases on a 360K drive. This may written on by a 360K
drive as well and still work on a 360K.
2. Once a disk has been written on first by a 360K drive
and then a 1.2M, it can only be read on a 1.2M drive!
That's life.
No, that's wrong. At least, it's not necessarily true.
I have formatted disks for an RX50 on the 1.2MB drive, written data
to them on that drive, and used them on a PDP-11. I have also used
floppies to back up an RSX-11S disk on "real" RX50 disks, transcribed
that to PC, overwritten them on the PC without a low-level format, and
read them on the PDP-11. I have had some floppies fail, but they
always failed either on the RX50 drive *before* they were ever in the
1.2MB drive, or they failed format on the 1.2MB drive before they ever
made it to the PDP-11.
I don't doubt the information I'm reading, that the track written
by the 1.2MB drive is narrower than the track written by a native 360K
drive. I'll even stipulate that my experience is limited to writing
disks for PDP-11s and the Altos 580 (DSQD I think; I haven't played
with that box in a long while), so I can't speak to the reliability on
other platforms.
5:34 p.m.
Patrick Finnegan wrote:
Doc Shipley declared on Monday 17 January 2005 11:04
pm:
Oh.
<Emily LaTella>
Never mind.
<Emily>
Doc
Dwight K. Elvey wrote:
Umm, the RX50s and Altos 580 floppies you've used are 80-track (96tpi)
disks just like 1.2MB floppies. 360k floppies are 40-track (48tpi)
disks. So, they're the same track width as a 1.2MB disk, not a 360k
disk. 1. A truely blank disk ( bulk erased ) can be
formatted
and written on by a 1.2M drive and will work in most
cases on a 360K drive. This may written on by a 360K
drive as well and still work on a 360K.
2. Once a disk has been written on first by a 360K drive
and then a 1.2M, it can only be read on a 1.2M drive!
That's life.
No, that's wrong. At least, it's not necessarily true.
I have formatted disks for an RX50 on the 1.2MB drive, written data
to them on that drive, and used them on a PDP-11. I have also used
floppies to back up an RSX-11S disk on "real" RX50 disks, transcribed
that to PC, overwritten them on the PC without a low-level format, and
read them on the PDP-11. I have had some floppies fail, but they
always failed either on the RX50 drive *before* they were ever in the
1.2MB drive, or they failed format on the 1.2MB drive before they ever
made it to the PDP-11.
I don't doubt the information I'm reading, that the track written
by the 1.2MB drive is narrower than the track written by a native 360K
drive. I'll even stipulate that my experience is limited to writing
disks for PDP-11s and the Altos 580 (DSQD I think; I haven't played
with that box in a long while), so I can't speak to the reliability on
other platforms. 
18 Jan
18 Jan
1:42 p.m.
Umm, the RX50s and Altos 580 floppies you've used
are 80-track (96tpi)
disks just like 1.2MB floppies. 360k floppies are 40-track (48tpi)
disks. So, they're the same track width as a 1.2MB disk, not a 360k
disk.
To be _really_ pedantic, both are 80 track disks.
The normal PC 360K disk is 40 _cylinders_ with 2 tracks per cylinder
(double sided), 48tpi (should this strictly be 48 cpi?)
The RX50 is 80 _cylinders_, 1 track per cylinder (single sided), 96 tpi.
It's the number of cylinders that matters.
-tony
17 Jan
17 Jan
6:53 p.m.
Doc wrote:
I have formatted disks for an RX50 on the 1.2MB
drive, written data
to them on that drive, and used them on a PDP-11. I have also used
floppies to back up an RSX-11S disk on "real" RX50 disks, transcribed
that to PC, overwritten them on the PC without a low-level format, and
read them on the PDP-11. I have had some floppies fail, but they always
failed either on the RX50 drive *before* they were ever in the 1.2MB
drive, or they failed format on the 1.2MB drive before they ever made it
to the PDP-11.
RX50 and PC 1.2M formats are both 96 TPI, so this says exactly
*nothing* about whether you can use 1.2M drives to write 360K disks
reliably (which you can't).
I *can* say that in writing, overwriting,
transcribing, and reading
RX50[0] floppies between a real PDP-11 and a Linux PC with a 1.2MB 5.25"
drive, track width has never been an issue.
Because they're identical. Nothing to do with PC 360K format.
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ard＠p850ug1.demon.co.uk -
doc＠mdrconsult.com -
dwight.elvey＠amd.com -
eric＠brouhaha.com -
pat＠computer-refuge.org