30 Aug
2001
30 Aug
'01
4:10 a.m.
For those who asked, I need DSDD 8" Soft-Sectored Disks.
Peace... Sridhar
31 Aug
31 Aug
1:42 a.m.
Absurdly Obtuse wrote:
For those who asked, I need DSDD 8" Soft-Sectored
Disks.
Jerome Fine replies:
I don't know if this will help, but here goes.
I was using the DSD 880/30 - an RL02/RX02 compatible. It
holds a single 8" floppy drive which can use both SSDD and DSDD
diskettes (soft-sectored). I found that since I had a small number of
DSDD diskettes and the media seemed to be identical, the ONLY
difference that I could observe was that the index hole was in a
different location.
I wired a DPDT switch into the index hole detection circuit. In the left
hand position, it was wired to duplicate the existing circuit. When I
wanted to REVERSE the operation, I used the right hand position of
the switch. In the second position, the index hole for a SSDD diskette
caused the drive to route the signal from the sensor to the portion of
the circuit which normally detected the signal from the DSDD index
hole. Thus, the drive and the software "THOUGHT" that a DSDD
media was present and I was able to use a SSDD diskette as a DSDD
diskette without having to punch a second set of index holes. The
use of a DSDD diskette as a SSDD diskette is also possible if that
is useful - I never found it to be needed.
Naturally, this required that I do a LLF (Low Level Format) on both
sides of the diskette. This the DSD 888/30 is able to do all by itself
and that solved the problem. As for using the DSDD diskette with
DEC software, V4.00 of RT-11 had some code which showed how
to access the "second" side and use the floppy drive as an RX03.
I used that code as a starting point since I also wanted to allow the
DYX.SYS device driver in a 22-bit environment with V5.03 of
RT-11. Note that the DSD 880/30 and the DEC RX02 with an
M8029 can use only the first 1/4 MByte (18 bit addresses) when
a transfer is made to/from the DMA silo from/into a buffer in the
memory of a PDP-11. Software in the DYX.SYS device driver
is able to use all 4 MBytes of the PDP-11 physical address space
in a manner totally transparent to the user of the device driver.
I realize that Sridhar is not using RT-11, but I just thought I might
mention the above for those of you that do.
Sincerely yours,
Jerome Fine
2:41 a.m.
Well, if the written spec's can be believed, you can't SEE the difference
between DD and SD media. That doesn't change the fact that they have different
spec's. Further, DS media are certified on BOTH sides, while the emulsion on
one side may be defective.
It's true that DS media have their index hole located differently than SS media.
The index timing is different, according to some drive makers, albeit not VERY
different. At least one mfg spec's the DS drives with 160 microsecond +/- 50
from the start of /Index to the data burst, while SS
media are at 200. I've
never given much thought to this and how it affects
things, but I am not
comfortable with the notion of switching, mechanically, between the two sensors.
Dick
----- Original Message -----
From: "Jerome Fine" <jhfine(a)idirect.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, August 31, 2001 7:42 AM
Subject: Re: 8" Floppies
Absurdly Obtuse
wrote:
For those who asked, I need DSDD 8"
Soft-Sectored Disks.
Jerome Fine replies:
I don't know if this will help, but here goes.
I was using the DSD 880/30 - an RL02/RX02 compatible. It
holds a single 8" floppy drive which can use both SSDD and DSDD
diskettes (soft-sectored). I found that since I had a small number of
DSDD diskettes and the media seemed to be identical, the ONLY
difference that I could observe was that the index hole was in a
different location.
I wired a DPDT switch into the index hole detection circuit. In the left
hand position, it was wired to duplicate the existing circuit. When I
wanted to REVERSE the operation, I used the right hand position of
the switch. In the second position, the index hole for a SSDD diskette
caused the drive to route the signal from the sensor to the portion of
the circuit which normally detected the signal from the DSDD index
hole. Thus, the drive and the software "THOUGHT" that a DSDD
media was present and I was able to use a SSDD diskette as a DSDD
diskette without having to punch a second set of index holes. The
use of a DSDD diskette as a SSDD diskette is also possible if that
is useful - I never found it to be needed.
Naturally, this required that I do a LLF (Low Level Format) on both
sides of the diskette. This the DSD 888/30 is able to do all by itself
and that solved the problem. As for using the DSDD diskette with
DEC software, V4.00 of RT-11 had some code which showed how
to access the "second" side and use the floppy drive as an RX03.
I used that code as a starting point since I also wanted to allow the
DYX.SYS device driver in a 22-bit environment with V5.03 of
RT-11. Note that the DSD 880/30 and the DEC RX02 with an
M8029 can use only the first 1/4 MByte (18 bit addresses) when
a transfer is made to/from the DMA silo from/into a buffer in the
memory of a PDP-11. Software in the DYX.SYS device driver
is able to use all 4 MBytes of the PDP-11 physical address space
in a manner totally transparent to the user of the device driver.
I realize that Sridhar is not using RT-11, but I just thought I might
mention the above for those of you that do.
Sincerely yours,
Jerome Fine
8:52 a.m.
On Fri, 31 Aug 2001, Richard Erlacher wrote:
Well, if the written spec's can be believed, you
can't SEE the difference
between DD and SD media. That doesn't change the fact that they have different
spec's. Further, DS media are certified on BOTH sides, while the emulsion on
one side may be defective.
It's true that DS media have their index hole located differently than SS media.
The index timing is different, according to some drive makers, albeit not VERY
different. At least one mfg spec's the DS drives with 160 microsecond +/- 50
from the start of /Index to the data burst, while SS media are at 200. I've
never given much thought to this and how it affects things, but I am not
comfortable with the notion of switching, mechanically, between the two sensors.
Dick
Probably of little consequence, Dick, since his DSDD disks will not be
readable by anyone else unless the have performed the same modification
to a single-sided drive.
- don
----- Original Message -----
From: "Jerome Fine" <jhfine(a)idirect.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, August 31, 2001 7:42 AM
Subject: Re: 8" Floppies
Absurdly
Obtuse wrote:
For those who asked, I need DSDD 8"
Soft-Sectored Disks.
Jerome Fine replies:
I don't know if this will help, but here goes.
I was using the DSD 880/30 - an RL02/RX02 compatible. It
holds a single 8" floppy drive which can use both SSDD and DSDD
diskettes (soft-sectored). I found that since I had a small number of
DSDD diskettes and the media seemed to be identical, the ONLY
difference that I could observe was that the index hole was in a
different location.
I wired a DPDT switch into the index hole detection circuit. In the left
hand position, it was wired to duplicate the existing circuit. When I
wanted to REVERSE the operation, I used the right hand position of
the switch. In the second position, the index hole for a SSDD diskette
caused the drive to route the signal from the sensor to the portion of
the circuit which normally detected the signal from the DSDD index
hole. Thus, the drive and the software "THOUGHT" that a DSDD
media was present and I was able to use a SSDD diskette as a DSDD
diskette without having to punch a second set of index holes. The
use of a DSDD diskette as a SSDD diskette is also possible if that
is useful - I never found it to be needed.
Naturally, this required that I do a LLF (Low Level Format) on both
sides of the diskette. This the DSD 888/30 is able to do all by itself
and that solved the problem. As for using the DSDD diskette with
DEC software, V4.00 of RT-11 had some code which showed how
to access the "second" side and use the floppy drive as an RX03.
I used that code as a starting point since I also wanted to allow the
DYX.SYS device driver in a 22-bit environment with V5.03 of
RT-11. Note that the DSD 880/30 and the DEC RX02 with an
M8029 can use only the first 1/4 MByte (18 bit addresses) when
a transfer is made to/from the DMA silo from/into a buffer in the
memory of a PDP-11. Software in the DYX.SYS device driver
is able to use all 4 MBytes of the PDP-11 physical address space
in a manner totally transparent to the user of the device driver.
I realize that Sridhar is not using RT-11, but I just thought I might
mention the above for those of you that do.
Sincerely yours,
Jerome Fine
9:32 a.m.
On Fri, 31 Aug 2001, Don Maslin wrote:
On Fri, 31 Aug 2001, Richard Erlacher wrote:
Oops! Obviously, I meant and should have said "double-sided drive".
- don
Well, if the written spec's can be believed,
you can't SEE the difference
between DD and SD media. That doesn't change the fact that they have different
spec's. Further, DS media are certified on BOTH sides, while the emulsion on
one side may be defective.
It's true that DS media have their index hole located differently than SS media.
The index timing is different, according to some drive makers, albeit not VERY
different. At least one mfg spec's the DS drives with 160 microsecond +/- 50
from the start of /Index to the data burst, while SS media are at 200. I've
never given much thought to this and how it affects things, but I am not
comfortable with the notion of switching, mechanically, between the two sensors.
Dick
Probably of little consequence, Dick, since his DSDD disks will not be
readable by anyone else unless the have performed the same modification
to a single-sided drive.
- don
3:28 p.m.
Well, what I apparently missed is that the intent was to use both sides of a
diskette in a single-sided drive, right? That is the only way that the
direction would have been reversed. It seems to me that DEC did rotate the data
in opposite directions in opposite sides on some models, didn't they? I've
never tried to use a floppy on a DEC machine, so I plead ignorance.
I'm not at all sure how any of this stuff would work out otherwise.
Incidentally, for 8" media at least, (since there's little confusion about
rotational rate and data rate) there's no reason why there has to be any
difference between SD and DD media, since the flux reversal density is the same
in FM as in MFM. The certification of the media for two-sided use, however, is
important, since it's conceivable that one side of a SS diskette could have a
contaminated emulsion, which would certainly be a defect disqualifiying it for
the two-sided use. VERY old drives needed nearly 250 ns of precompensation,
however, while newer ones needed between 125 and 180. I typically used a 6 MHz
oscillator to time the precomp on 8" diskettes, and that worked out remarkably
over a wide range of drives.
Back in the '70s diskettes often were priced at nearly $10 each, and we often
tried to save a buck or two by punching holes in the appropriate place in a SS
diskette's jacket in order to make it work as DS. This worked better than half
of the time. Punching the hole so the "other" side of a SS diskette could be
used SS produced disappointing results too. Neither approach was useable for
work paid for by others. I think that's because emulsions did get messed up
Oops! Obviously, I meant and should have said "double-sided drive".
- don
from time to time, and weren't applied to both
sides at the same time. Maybe
that's not right, but there must have been some
reason.
Dick
----- Original Message -----
From: "Don Maslin" <donm(a)cts.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, August 31, 2001 3:32 PM
Subject: Re: 8" Floppies
On Fri, 31 Aug 2001, Don Maslin wrote:
>
>
> On Fri, 31 Aug 2001, Richard Erlacher wrote:
>
> > Well, if the written spec's can be believed, you can't SEE the
difference
> > between DD and SD media. That doesn't change the fact that they have
different
> > spec's. Further, DS media are certified
on BOTH sides, while the emulsion
on
> > one side may be defective.
> >
> > It's true that DS media have their index hole located differently than SS
media.
> > The index timing is different, according to
some drive makers, albeit not
VERY
> > different. At least one mfg spec's the
DS drives with 160 microsecond +/-
50
> > from the start of /Index to the data burst,
while SS media are at 200.
I've
> > never given much thought to this and how it
affects things, but I am not
> > comfortable with the notion of switching, mechanically, between the two
sensors.
Dick
Probably of little consequence, Dick, since his DSDD disks will not be
readable by anyone else unless the have performed the same modification
to a single-sided drive.
- don
1 Sep
1 Sep
5:45 a.m.
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6:37 a.m.
Tony Duell wrote:
You might be thinking of the RX50 dual 5.25"
drive. This is a
single-sided unit which takes 2 separate floppy disks. They rotate in
opposite directions (due to a belt that runs over both sides of the
chassis) but as the lower disk is inserted label side down, in fact each
disk rotates the 'standard' way and can be read/written on other machines
without problems.
Jerome Fine replies:
But as far as the head is concerned, the direction of rotation is the same
on a relative basis - which is why a floppy written in the top drive
can still be read in the bottom drive.
Actually, I think the best use for an RX50 drive is what my grandson
did one day - took a VERY LARGE SLEDGE HAMMER and ...
Other than a CPU, DEC never seemed to manage to make decent
hardware the first time around. Even the software had bugs that
were really dumb. Of course, compared with M$, DEC software
was Platinum compared to Tin (is there anything less than tin?).
[But since DEC was bought in 1996?, that is OT]
I've never seen a floppy drive that reverses the
direction of the spindle
rotation when side 1 is selected.
Actually, just for fun, one day I punched the extra holes into an RX50
floppy, turned it over (did a Low Level Format in a different drive)
and ran it as a flippy - I still have a couple that I use for demos.
So instead of reversing the direction of the spindle, I reversed the
direction of the media (Grin>).
Sincerely yours,
Jerome Fine
8 a.m.
At 02:37 PM 9/1/01 -0400, you wrote:
Jerome Fine replies:
Other than a CPU, DEC never seemed to manage to make decent
hardware the first time around. Even the software had bugs that
were really dumb. Of course, compared with M$, DEC software
was Platinum compared to Tin (is there anything less than tin?).
[But since DEC was bought in 1996?, that is OT]
Dec didn't design the RX50... DEC bought out another company that
originally designed the drive (IIRC) and they had a warehouse of the
drives, unused and dev put them to use.
8:05 a.m.
New subject: DEC Design
Jerome Fine replies:
Actually, I think the best use for an RX50 drive is
what my grandson
did one day - took a VERY LARGE SLEDGE HAMMER and ...
Yup.
They really bit and everyone at DEC new it.
Other than a CPU, DEC never seemed to manage to make decent
hardware the first time around. Even the software had bugs that
were really dumb. Of course, compared with M$, DEC software
was Platinum compared to Tin (is there anything less than tin?).
[But since DEC was bought in 1996?, that is OT]
Actually, DEC's tape drives were abysmal in design (not counting the
DECtapes which were really reel-to-reel disk drives.
Their disks had no more bugs than anyone elses and they were just on the
pricey side.
The RL0x's were pretty slick and the RK05/6/7's were ok. RM80's needed
the RA81's 400+meg hda to be competitive... The RA81's would've been
nice if the breather glue problem didn't occur.
The DEC stuff was always pretty good maintenance wise with good diags
and offline capabilities and testers.
Lots of other manufacturers didn't do as well in this area -- but DEC
milked the prices a bit too much and spawned a plug-compatible push
which their Massbus patents killed.
Bill
--
Bill Gates is a Persian cat and a monocle away from being a
villain in a James Bond movie -- Dennis Miller
bpechter@shell.monmouth.com|pechter@pechter.dyndns.org
2 Sep
2 Sep
12:02 p.m.
New subject: DEC Design
Bill Pechter wrote:
Jerome Fine
replies:
Actually, I think the best use for an RX50 drive is what my grandson
did one day - took a VERY LARGE SLEDGE HAMMER and ...
Yup. They really bit and
everyone at DEC new it. Other than a
CPU, DEC never seemed to manage to make decent
hardware the first time around. Even the software had bugs that
were really dumb. Of course, compared with M$, DEC software
was Platinum compared to Tin (is there anything less than tin?).
[But since DEC was bought in 1996?, that is OT]
Actually, DEC's tape drives
were abysmal in design (not counting the
DECtapes which were really reel-to-reel disk drives. Their disks had no more bugs than anyone elses and
they were just on the
pricey side.
Think of the RC25!! I know that is not a good example, but...
The RL0x's were pretty slick and the
RK05/6/7's were ok. RM80's needed
the RA81's 400+meg hda to be competitive... The RA81's would've been
nice if the breather glue problem didn't occur.
I agree that the RL02 was finally a reasonable drive and not out of line
with DEC standards as far as price.
The DEC stuff was always pretty good maintenance wise
with good diags
and offline capabilities and testers.
When the drive was basically OK and worked in the first place - the RC25 again.
Yes I agree it was an isolated example. I don't think that even the TK50 was as bad.
Lots of other manufacturers didn't do as well in
this area -- but DEC
milked the prices a bit too much and spawned a plug-compatible push
which their Massbus patents killed.
The BIbus was another example.
What DEC seemed to never be able to understand was that co-operation
produced more benefit than attempting to hog all of the market for just
their own benefit. From a close understanding of one VAR in Toronto
who was selling 80% DEC in 1985 and 20% DEC by 1988, DEC shot
themselves in the foot (i.e. Ken Olsen and his VPs) probably without even
realizing it. So when Olsen (was forced?) left, the shell had already
collapsed. And while the PDP-11 and VMS might have rescued DEC
if the marketing had changed, there seemed to be too much inertia to
make the needed changes.
I always had a joke about that:
"What was DEC's marketing policy around 1985?"
Add nothing! - Buy the product elsewhere - add a ZERO to the price
(on the right hand side) and resell it.
"What was DEC's hardware policy around 1985?"
The same - add nothing! Buy a Micropolis 1325 and add that ZERO ohm
resistor so it could be formatted by an RQDX2,3.
I realize these are bad jokes, but the kernel of truth is there. Of course I have
the same joke about Honeywell and their thermostat for my AC. Differences were:
(a) Decal was changed from "HEAT/OFF" to "COOL/OFF/HEAT"
(b) Doubled the price from one function to two
(c) Removed a bolt from the actuator arm to allow the third position to be used.
Also Seagate did the same with their 20/40 MByte disk drives!
So DEC was no more predatory that M$ in many ways, they were just too
stupid to realize that it does not pay in the long run if you don't have enough
clout.
Plus, those third party VARs sold a lot of software for DEC until they were cut
off - also stupid!
Sincerely yours,
Jerome Fine
4 Sep
4 Sep
3:32 a.m.
New subject: DEC Design
--- Jerome Fine <jhfine(a)idirect.com> wrote:
Do you mean the TU-58? I am looking for one!!
The TU-58 is also known as "DECtape-II". The original poster was
referring to TU-55/TU-56 DECtape. Like the TU-58, they are a block-
addressable magtape, but they are open reel, not cassette.
I have one that does not work and I want to replace
the bad part.
Electrical or mechanical?
The rollers are OK.
That'll change. I've had to replace every roller I have. 30cm of
that tygon tubing Allison recommended is pretty cheap.
This is the external TU-58 with two drives in a black
box. Does anyone
have one?
Not me. I've never had the proper table-top unit. I have a TU-58 in each
11/750, a dual unit in the 11/730, a VT-103, and I have a homemade "table-
top" unit that was from an 11/725 that my employer stripped for parts back
when it was cheaper to buy an 11/725 to keep our 11/730 running that it was
to pay DEC maintenance; that plus a couple of drive mechanisms in a pair of
old HP serial line analyzers. (The 11/725 was completely stripped about
10 years ago, and the innards replaced with a 68000 analyzer from Northwest
Instruments for portability around the shop).
I've been using the homeless unit to read in ancient DEC software
distributions. It's in a long steel box (from the VAX); I made a power
cable for so I can run it off the PeeCee power supply. Just this weekend,
I found another cache of tapes - 11/750 diags and more VMS 3.x upgrade
distros.
-ethan
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1 Sep
1 Sep
8:23 a.m.
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7:07 a.m.
No ... What some folks used to do is punch a second index hole such that the
diskette could be used on both sides, albeit one side at a time, in a SS drive.
In order to make that work the diskette has to be put in backwards, i.e, such
that the opposite side of the diskette faces the head as is normally the case,
in which orientation the diskette is rotating in the opposite direction with
respect to the head from that in which it would be if it were in a DS drive,
which has a head on each side.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Saturday, September 01, 2001 11:45 AM
Subject: Re: 8" Floppies
>
> Well, what I apparently missed is that the intent was to use both sides of a
> diskette in a single-sided drive, right? That is the only way that the
> direction would have been reversed. It seems to me that DEC did rotate the
data
in opposite
directions in opposite sides on some models, didn't they? I've
never tried to use a floppy on a DEC machine, so I plead ignorance.
You might be thinking of the RX50 dual 5.25" drive. This is a
single-sided unit which takes 2 separate floppy disks. They rotate in
opposite directions (due to a belt that runs over both sides of the
chassis) but as the lower disk is inserted label side down, in fact each
disk rotates the 'standard' way and can be read/written on other machines
without problems.
I've never seen a floppy drive that reverses the direction of the spindle
rotation when side 1 is selected.
-tony
31 Aug
31 Aug
2:41 p.m.
Richard Erlacher wrote:
Well, if the written spec's can be believed, you
can't SEE the difference
between DD and SD media. That doesn't change the fact that they have different
spec's. Further, DS media are certified on BOTH sides, while the emulsion on
one side may be defective.
Jerome Fine replies:
Then some more information may be helpful. Note that since this is only my
own experience, it might have been different for others if they had installed
the same switch. However, since I believe that 8" floppies are no longer very
popular, it is unlikely that this information will actually be put to the test.
Over about 5 year from 1988 to 1993, I formatted about 900 SSDD diskettes
from about a dozen manufactures as DSDD. They were my
PRIMARY
backup and I still have a number which I need to transfer to a hard disk
drive.
I seem to remember that ALL SSDD floppies that I attempted to format
as DSDD floppies in the DSD 880/30 worked except for some from one
particular manufacturer that were done in 1993. At the very end, I acquired
(rescued from pile on the way to the dumptser - i.e. still inside the building
in a normal environment, so storage conditions would NOT have caused a
problem) a couple of dozen of DEC diskettes with software for RSX-11.
(Sorry, back 8 years ago, I did not realize that they might have been worth
something.) About half of the DEC diskettes would not format correctly.
After the format operation was finished, I always did a READ check of
every block. What was interesting was that when there was a problem,
it was on the original side of the floppy and the so-called second side was OK.
The other bit of information is that when these SSDD floppies were sometimes
used again in a DEC RX02 drive, there was NEVER any problem with the
original side - except of course with some of the DEC floppies.
It's true that DS media have their index hole
located differently than SS media.
The index timing is different, according to some drive makers, albeit not VERY
different. At least one mfg spec's the DS drives with 160 microsecond +/- 50
from the start of /Index to the data burst, while SS media are at 200. I've
never given much thought to this and how it affects things, but I am not
comfortable with the notion of switching, mechanically, between the two sensors.
Dick
Since I had no specs, I just tried it. It worked. Not one floppy that was formatted
as DSDD was unable to be used in a DEC RX02 drive. In addition, one some of
the SSDD floppies (before I had installed the switch) I have punched a second
set of holes in the DSDD index position. I initially covered up the SSDD index
holes, but found that these same floppies worked without a problem in both the
DSD 8" "dual" drive and a DEC RX02 drive. I never worked out the timing
between the two index holes, but since they are about 1/2" apart, it should be
trivial based on the number of revolutions per second. The distance from the
centre of the floppy at that location is about 1 1/2" (from memory - it is probably
between 1" and 2"). At 300 rpm or PIE * 3" * 6 per second = about 50"
per second,
I get a timing difference of 10 milliseconds. Since 1/10" is still about 2
milliseconds,
I suspect that any timing requirements less than 1/2 milliseconds would be too
difficult to meet. Of course, my calculations might be totally wrong.
As far as the comment from: Don Maslin
Probably of little consequence, Dick, since his DSDD disks will not be
readable by anyone else unless the have performed the same modification
to a single-sided drive.
Oops! Obviously, I meant and should have said "double-sided drive".
As I mentioned above, the so-called first side could always be accessed
via a single-sided DEC RX02 or any other single-sided drive. As for an
unmodified double-sided drive, I have one on an SMS-1000 box that is
very interesting. It uses 8" floppies and is also both single-sided and
double-sided in operation in that it senses both index hole locations.
However, it is VERY different in operation. FIRST, although it obviously
uses the same interleave scheme as DEC, the emulation is MSCP, i.e.
in RT-11 it uses the DEC DUX.SYS device driver. The first time I
tried to boot RT-11, I was stumped. Finally it dawned on me. On
the DSD 880/30, I did the command:
COPY/BOOT:DU DY0:RT11XM.SYS DY0:
with a SSDD floppy that had RT11XM.SYS and both the DYX.SYS
and DUX.SYS device drivers. Worked just fine. SECOND, although
the number of blocks is 988 in single sided-mode and 1976 in double-sided
mode, in double-sided mode the second side is accessed right after the
same track for the first side. Which means that since the DYX.SYS
device driver on the DSD 880/30 accesses first all 988 blocks on one
side and then all of the 988 blocks on the other side, the same DSDD
floppy can't be used on both systems. If the 8" floppy is used to transfer
any files in RT-11, I can use ONLY SSDD media after which I can
write the contents of two SSDD floppies to one DSDD floppy from
a temporary file since the SMS-1000 has only one 8" drive.
All of the above is very much in the past over 10 years ago and I have
probably not touched an 8" floppy in many years except to send some
with TCP/IP to the UK.
So, yes Tony, I do play with hardware to some extent, but only in direct
relationship to a software need.
Sincerely yours,
Jerome Fine
----- Original Message -----
From: "Jerome Fine" <jhfine(a)idirect.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, August 31, 2001 7:42 AM
Subject: Re: 8" Floppies
> >Absurdly Obtuse wrote:
>
> > For those who asked, I need DSDD 8" Soft-Sectored Disks.
>
> Jerome Fine replies:
>
> I don't know if this will help, but here goes.
>
> I was using the DSD 880/30 - an RL02/RX02 compatible. It
> holds a single 8" floppy drive which can use both SSDD and DSDD
> diskettes (soft-sectored). I found that since I had a small number of
> DSDD diskettes and the media seemed to be identical, the ONLY
> difference that I could observe was that the index hole was in a
> different location.
>
> I wired a DPDT switch into the index hole detection circuit. In the left
> hand position, it was wired to duplicate the existing circuit. When I
> wanted to REVERSE the operation, I used the right hand position of
> the switch. In the second position, the index hole for a SSDD diskette
> caused the drive to route the signal from the sensor to the portion of
> the circuit which normally detected the signal from the DSDD index
> hole. Thus, the drive and the software "THOUGHT" that a DSDD
> media was present and I was able to use a SSDD diskette as a DSDD
> diskette without having to punch a second set of index holes. The
> use of a DSDD diskette as a SSDD diskette is also possible if that
> is useful - I never found it to be needed.
>
> Naturally, this required that I do a LLF (Low Level Format) on both
> sides of the diskette. This the DSD 888/30 is able to do all by itself
> and that solved the problem. As for using the DSDD diskette with
> DEC software, V4.00 of RT-11 had some code which showed how
> to access the "second" side and use the floppy drive as an RX03.
> I used that code as a starting point since I also wanted to allow the
> DYX.SYS device driver in a 22-bit environment with V5.03 of
> RT-11. Note that the DSD 880/30 and the DEC RX02 with an
> M8029 can use only the first 1/4 MByte (18 bit addresses) when
> a transfer is made to/from the DMA silo from/into a buffer in the
> memory of a PDP-11. Software in the DYX.SYS device driver
> is able to use all 4 MBytes of the PDP-11 physical address space
> in a manner totally transparent to the user of the device driver.
>
> I realize that Sridhar is not using RT-11, but I just thought I might
> mention the above for those of you that do.
>
> Sincerely yours,
>
> Jerome Fine
>
>
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