21 Nov
2014
21 Nov
'14
10:13 a.m.
Where can I get RX01 SSSD 8" floppies?
Used are fine.
--
Michael Thompson
21 Nov
21 Nov
11:26 a.m.
On Fri, Nov 21, 2014 at 10:13 AM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
Where can I get RX01 SSSD 8" floppies?
Used are fine.
Is it correct that RX01 format floppies can be created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
12:30 p.m.
On 11/21/2014 2:26 PM, Glen Slick wrote:
On Fri, Nov 21, 2014 at 10:13 AM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
Yes. RX01 (which I have and use) are
standard IBM -- straight FM encoding,
128 bytes /sector.
- JS.
Where can I get RX01 SSSD 8" floppies?
Used are fine.
Is it correct that RX01 format floppies can be created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
12:40 p.m.
On 11/21/2014 11:26 AM, Glen Slick wrote:
Is it correct that RX01 format floppies can be created
from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
Yup. The RX02 ("double density") use a whacky MFM scheme (with some
code substitutions) for data with FM sector headers. Not doable at all
with a standard PC setup. RX01s are pretty much stock FM.
--Chuck
12:44 p.m.
Is it correct that RX01 format floppies can be
created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
Yup. The RX02 ("double density") use a whacky MFM scheme (with some
code substitutions) for data with FM sector headers. Not doable at all
with a standard PC setup. RX01s are pretty much stock FM. 
4:28 p.m.
On 2014-11-21 12:44, tony duell wrote:
I seem to remember that if you format an 8" floppy, single sided, single density
'IBM3740 format' (the standard one, 77 tracks, 26 sectors/track, 128
bytes/sector)
then at least an RX02, and probably an RX01 can be convinced to put the DEC
type directory, etc. on it. An RX02 can re-format it as MMFM too.
Of course. You don't even need to do any convincing. A directory (which
differs between different OSes) can always be written. That is just
bytes of data on the floppy.
Is it correct that RX01 format floppies can be
created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
Yup. The RX02 ("double density") use a whacky MFM scheme (with some
code substitutions) for data with FM sector headers. Not doable at all
with a standard PC setup. RX01s are pretty much stock FM. Most CP/M machines with 8" drives can do the
intial format
I should probably point out that an RX01 or RX02 cannot actually format
floppies at all. They need preformatted floppies, in the IBM format.
Johnny
4:54 p.m.
On 11/21/2014 04:28 PM, Johnny Billquist wrote:
I should probably point out that an RX01 or RX02
cannot actually format
floppies at all. They need preformatted floppies, in the IBM format.
Rainbow 100 floppies were initially like that--you bought formatted
media. But very quickly, someone wrote a formatting program.
But you really have to wonder what DEC was thinking...
--Chuck
9:59 p.m.
On 2014-11-21 16:54, Chuck Guzis wrote:
On 11/21/2014 04:28 PM, Johnny Billquist wrote:
Yeah. The RX50. The Rainbow was the one machine that apparently was
capable of actually formatting them. But lots of other DEC machines used
them.
I should probably point out that an RX01 or RX02
cannot actually format
floppies at all. They need preformatted floppies, in the IBM format.
Rainbow 100 floppies were initially like that--you bought formatted
media. But very quickly, someone wrote a formatting program. But you really have to wonder what DEC was thinking...
Indeed. But on the other hand, it was probably a good source of income
for them, selling preformatted floppies...
Johnny
22 Nov
22 Nov
5:57 a.m.
On Friday (11/21/2014 at 09:59PM -0800), Johnny Billquist wrote:
On 2014-11-21 16:54, Chuck Guzis wrote:
FWIW, the Heathkit H27 can low-level format RX01 media. There is a switch
on the front to enable the formatting.
http://www.computermuseum.li/Testpage/Heathkit-DEC-H11.htm
The H-27 floppy disk subsystem features two 256K 8" single side,
single density drives. The drives are DEC RX01 compatible,
and, unlike the DEC products of the day, are able to format
the floppies,.
There is another switch to select between "EXTENDED" and "RX01" and I
am
still trying to determine if "EXTENDED" is RX02 or something proprietary
to Heath.
I have an H27 but it is not running currently and I do not have a manual.
--
Chris Elmquist
On 11/21/2014 04:28 PM, Johnny Billquist wrote:
Yeah. The RX50. The Rainbow was the one machine that apparently was capable
of actually formatting them. But lots of other DEC machines used them.
I should probably point out that an RX01 or RX02
cannot actually format
floppies at all. They need preformatted floppies, in the IBM format.
Rainbow 100 floppies were initially like that--you bought formatted
media. But very quickly, someone wrote a formatting program. But you really have to wonder what DEC was
thinking...
Indeed. But on the other hand, it was probably a good source of income for
them, selling preformatted floppies...
21 Nov
21 Nov
1:08 p.m.
On Fri, Nov 21, 2014 at 12:40 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 11/21/2014 11:26 AM, Glen Slick wrote:
So is the original poster (Michael) really looking for already
formatted RX01 floppies, or will blank 8-inch single sided floppies do
just as well? Probably easier to find generic floppies than already
formatted RX01 floppies.
Is it correct that RX01 format floppies can be
created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
Yup. The RX02 ("double density") use a whacky MFM scheme (with some code
substitutions) for data with FM sector headers. Not doable at all with a
standard PC setup. RX01s are pretty much stock FM.
4:30 p.m.
On 2014-11-21 13:08, Glen Slick wrote:
On Fri, Nov 21, 2014 at 12:40 PM, Chuck Guzis
<cclist at sydex.com> wrote:
True. But if he find blank floppies, or floppies with some other format,
then he needs something else than a RX01/RX02 to reformat the floppies
before they can be used on an RX01/RX02.
Johnny
On 11/21/2014 11:26 AM, Glen Slick wrote:
So is the original poster (Michael) really looking for already
formatted RX01 floppies, or will blank 8-inch single sided floppies do
just as well? Probably easier to find generic floppies than already
formatted RX01 floppies. Is it correct that RX01 format floppies can be
created from blank
floppies with a standard PC floppy controller (or at least some
controllers / motherboards, depending on the controller chip) while
RX02 format floppies cannot?
Yup. The RX02 ("double density") use a whacky MFM scheme (with some code
substitutions) for data with FM sector headers. Not doable at all with a
standard PC setup. RX01s are pretty much stock FM.
7:48 p.m.
Michael Thompson wrote:
Where can I get RX01 SSSD 8" floppies?
Used are fine.
I should have realized that the situation needs to be clarified:
(a) As far as I know, (almost?) all soft sectored 8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option). In the latter case, the format
is essentially the same, but only the data portion of the sector is
double-density. In addition, while a DEC RX01 drive can use only
single-density media, a DEC RX02 drive can use BOTH single-
density (SSSD) AND double-density (SSDD) media which means
that the DEC RX02 drive can read / write media from a DEC RX01
drive - but can boot an RX01 media only if the boot block is first
changed from DX to DY.
(b) The IBM standard, the DEC RX01 and the DEC RX02 all
use ONLY single-sided media. The DY.MAC V04.00 device file
(the device driver for the DY.SYS file in RT-11) included (probably
never tested) code to support double-sided media which would have
used the DEC RX03 drive. At least a few of the third party drives
and controllers for the Qbus PDP-11 which could read / write 8"
floppy media actually supported both single-density and double-density
media that were BOTH single-sided (SSSD, SSDD) and double-sided
(DSSD, DSDD). However, at the moment, I can recall the name only
for the DSD 880/30 drive (Data Systems Design).
(c) The standard for single-sided media was to place the index hole
very close to the center of the jacket for the floppy media. For
double-sided media, the index hole was offset by about one inch.
HOWEVER, the DEC RX02 drive is always able to read / write
the first side of a double-sided media if there is an index hole in the
expected position for single-sided media. The DSD 880/30 is able
to always read both sides of a double-sided 8" media regardless of
which position is used for the index hole, BUT normally the DY: device
driver will detect the position of the index hole and make only the
first side of the media available if the hole is in the single-sided
position.
When the index hole is in the double-sided position, the DY: device
driver will detect the position of the index hole and make both sides
of the media available. HOWEVER, it is possible to modify the
function of the detection circuit (using a DPDT switch) and reverse
the functions of the index hole position - in that case, the RX03 drive
will support the use of both sides of the 8" media when the index hole
is in the single-sided
position!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
(Rather handy to flip the switch on the RX03 drive rather than punch
a new pair of holes on each single-sided media!!!!!!!!!!!!!!!!!!!!!!!)
(d) At least for the PDP-11 (and probably for all DEC hardware), it
was NOT possible to perform a Low Level Format (LLF) on 8"
floppy media using either the RX01 or the RX02 drive. What was
possible with the RX02 drive was to switch the media from single-
density to double-density and from double-density to single-density
AFTER the initial LLF was done on the 8" floppy media. Under RT-11,
the FORMAT command SOMETIMES seemed the be able to "rescue"
8" media with bad sectors using the FORMAT command when those
specific sectors on the media could no longer could be read or written.
I don't remember if that operation could also be done with the RX01
drive. HOWEVER, the 8" media would have had to already been
through an LLF first (SSSD).
(e) At least for the Data Systems Design 8" floppy drives, it was
possible to perform an LLF. For the DSD 880/30 hardware which
was composed of 3 * RL02 and a single RX03, it was possible to
take the unit off-line and perform any of the 4 possible LLF operations:
- SSSD
- DSSD
- SSDD
- DSDD
Have I left out any information? Are there still any questions?
Jerome Fine
8:53 p.m.
On 11/21/2014 07:48 PM, Jerome H. Fine wrote:
(a) As far as I know, (almost?) all soft sectored
8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option).
A couple of nits--the RX02 double-density data fields are not strictly
MFM. In other words, if you'd have a controller that supported standard
MFM recording and that could be switched to MFM mode after using FM for
the ID address header, it still wouldn't work.
DEC in its infinite zeal to be different, realized that certain MFM
patterns could be mistakenly recognized as FM address marks. So there
are some substitutions in the MFM coding to avoid these problem patterns.
Also, IBM-standard formatted "double density" media, i.e. S/36-style
always had the first track as FM, with the remainder MFM. Various
sector sizes were used, from 256 bytes to 1024.
FWIW,
Chuck
9:21 p.m.
Chuck Guzis wrote:
On 11/21/2014
07:48 PM, Jerome H. Fine wrote:
(a) As far as I know, (almost?) all soft
sectored 8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option).
A couple of nits--the RX02 double-density data fields are not strictly
MFM. In other words, if you'd have a controller that supported
standard MFM recording and that could be switched to MFM mode after
using FM for the ID address header, it still wouldn't work.
DEC in its infinite zeal to be different, realized that certain MFM
patterns could be mistakenly recognized as FM address marks. So there
are some substitutions in the MFM coding to avoid these problem patterns.
Also, IBM-standard formatted "double density" media, i.e. S/36-style
always had the first track as FM, with the remainder MFM. Various
sector sizes were used, from 256 bytes to 1024.
10:01 p.m.
On 11/21/2014 09:21 PM, Jerome H. Fine wrote:
One point to mention (or clarify) is that for DEC, the FORMAT
operation did NOT include writing the file structure. For the PC,
the FORMAT command does BOTH an LLF as well as writing
an initial root file structure (FAT16??) on the floppy media. But
for DEC hardware with both the RX01 and the RX02, writing
the file structure made use of the INITIALIZE command (at least
under RT-11 and something similar under RSTS/E and RSX-11).
So with DEC PDP-11 operating systems which used 8" floppy
media, the user understood very clearly the difference between
the FORMAT and INITIALIZE commands and what each one
did.
Sort of like Unix mkfs?
--Chuck
10:17 p.m.
On 2014-11-21 22:01, Chuck Guzis wrote:
On 11/21/2014 09:21 PM, Jerome H. Fine wrote:
Correct.
And to make yet another silly point. FORMAT on PCs often does not
actually do a low level format, but actually only creates a file system.
Johnny
One point to mention (or clarify) is that for DEC, the FORMAT
operation did NOT include writing the file structure. For the PC,
the FORMAT command does BOTH an LLF as well as writing
an initial root file structure (FAT16??) on the floppy media. But
for DEC hardware with both the RX01 and the RX02, writing
the file structure made use of the INITIALIZE command (at least
under RT-11 and something similar under RSTS/E and RSX-11).
So with DEC PDP-11 operating systems which used 8" floppy
media, the user understood very clearly the difference between
the FORMAT and INITIALIZE commands and what each one
did.
Sort of like Unix mkfs?
10:52 p.m.
On 11/21/2014 10:17 PM, Johnny Billquist wrote:
And to make yet another silly point. FORMAT on PCs
often does not
actually do a low level format, but actually only creates a file system.
With floppies, somewhere around DOS 5, the "quick" format was
introduced, which doesn't LLF unless the disk isn't recognized as a
FAT12 filesystem.
What I find irritating is that XP and later does its level best to
figure out what format, if any, is present on a floppy in response to a
FORMAT command. A minute or so may go by before XP figures out that the
disk isn't formatted at all. It's not strictly necessary--one can call
the appropriate NT API to format a track and off it goes. But I know of
no command-line switch to FORMAT to disable the check.
MSDOS 5 and 6 had a /u option on format that essentially said "I don't
care what's on it, just (low-level) format the darned thing!" But that
was dropped in the Windows 9x versions (MSDOS 7.x).
Linux was never wonderful with floppies, but has gotten much worse in
that latest versions, with both USB and legacy floppy drives. My only
conclusion is that it's because of utter neglect--and the nose in the
air attitude "what moron still uses floppies?"
Of course, hard drives under MSDOS and NT don't acknowledge any idea of
LLF--and indeed, for later drives, it's probably not implemented in the
drive interface.
CP/M as delivered from DRI in the OEM kit doesn't have a FORMAT command,
even in skeleton form. That's strictly up to the system vendor as to
whether one is implemented or not.
--Chuck
10:14 p.m.
On 2014-11-21 19:48, Jerome H. Fine wrote:
Incorrect. The RX02 cannot read standard 8" Double Density floppies. It
can only deal with single density floppies, just like the RX01.
The RX02 can deal with both RX01 and RX02 media. However, the software
(obviously) needs to know how to deal with it, as RX02 media gives you
256 bytes per sector, while RX01 media gives you 128 bytes per sector,
which is a significant difference that needs to be dealt with.
(And yes, the software can detect what format each sector is in.)
Johnny
Michael
Thompson wrote:
Where can I get RX01 SSSD 8" floppies?
Used are fine.
I should have realized that the situation needs to be clarified:
(a) As far as I know, (almost?) all soft sectored 8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option). In the latter case, the format
is essentially the same, but only the data portion of the sector is
double-density. In addition, while a DEC RX01 drive can use only
single-density media, a DEC RX02 drive can use BOTH single-
density (SSSD) AND double-density (SSDD) media which means
that the DEC RX02 drive can read / write media from a DEC RX01
drive - but can boot an RX01 media only if the boot block is first
changed from DX to DY.
22 Nov
22 Nov
5:14 p.m.
Johnny Billquist wrote:
On 2014-11-21
19:48, Jerome H. Fine wrote:
I should have realized that the situation needs
to be clarified:
(a) As far as I know, (almost?) all soft sectored 8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option). In the latter case, the format
is essentially the same, but only the data portion of the sector is
double-density. In addition, while a DEC RX01 drive can use only
single-density media, a DEC RX02 drive can use BOTH single-
density (SSSD) AND double-density (SSDD) media which means
that the DEC RX02 drive can read / write media from a DEC RX01
drive - but can boot an RX01 media only if the boot block is first
changed from DX to DY.
Incorrect. The RX02 cannot read standard 8" Double Density floppies.
It can only deal with single density floppies, just like the RX01.
10:09 p.m.
On 2014-11-22 17:14, Jerome H. Fine wrote:
I am quite sure that your information with regard to Double-Density
floppies is technically correct. Your much greater level of experience
must have acquainted you with actual double-density floppies at some
point. However, it would be helpful if you could provide a specific
example of a real double-density 8" floppy so that we can all share
the same information. The information which would be needed is
the name of the manufacturer of the floppies, the name of the computer
system, the name of the double-density drive, the name of the controller,
the name of the operating system and the name of the device driver used
when a "standard 8" Double Density floppy" is present. If you don't
have
all of the above information, present at least as much as you remember.
Also, at least an estimate of the percentage of "standard 8" Double
Density floppies" in use compared to the standard 8" IBM SSSD
floppies (including both DEC RX01 and DEC RX02) would be
useful so we can judge if "standard 8" Double Density floppies"
were significant. In my opinion, anything less that 1% would be
considered insignificant.
It is great to contradict what all DEC documentation on 8" RX02 floppies
mentions with respect to double-density media (and given that the DEC
documentation was usually complete and correct - DEC, in this case
much have been providing false information or at least characterizing
"double-density" incorrectly at least as far as you are concerned) and I
am sure that you do have some competing example in mind. What is it?
And why is the statement that DEC makes that the media are double-density
(when the sector size is 256 bytes) "incorrect"?
The RX02 is not a standard double density floppy. It is a single density
format floppy with a double density encoding for the data area of each
sector. That is a very different thing.
I have double density IBM floppies at home, and believe me, I have tried
using them in RX01 and RX02 drives. They obviously do not work.
But it should be obvious even without much more than a cursory glance at
the documentation for an RX02. There is no contradictions to what DEC
documented compared to what I wrote.
DEC RX02 floppies are really the same low level format as RX01 floppies.
There is a bit in the sector header for each block that is set to 1 if
the sector is actually in double density for an RX02, or 0 for single
density. I don't know if IBM themselves ever used that bit in the sector
header for anything, but DEC used it for this purpose, and it
documented. You can, on a per sector basis, use either single density or
double density. The low level format is always the same.
Johnny
Johnny
Billquist wrote:
On
2014-11-21 19:48, Jerome H. Fine wrote:
I should have realized that the situation needs
to be clarified:
(a) As far as I know, (almost?) all soft sectored 8" floppy media
are formatted as either single-density (which is the IBM standard -
also known as the DEC RX01 option) or double-density.(which
is the additional DEC RX02 option). In the latter case, the format
is essentially the same, but only the data portion of the sector is
double-density. In addition, while a DEC RX01 drive can use only
single-density media, a DEC RX02 drive can use BOTH single-
density (SSSD) AND double-density (SSDD) media which means
that the DEC RX02 drive can read / write media from a DEC RX01
drive - but can boot an RX01 media only if the boot block is first
changed from DX to DY.
Incorrect. The RX02 cannot read standard 8" Double Density floppies.
It can only deal with single density floppies, just like the RX01.
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