19 Dec
2025
19 Dec
'25
4:15 a.m.
No. The only DEC drive that had removable plus fixed
on the same spindle
was the RC25.
If I remember correctly it was Diablo that sold an RK05-compatible drive
with one fixed platter and one removable cartridge. I encountered it on a
PDP 11/34 running Mini Unix and then, hmmm, Unix v<something small>. (Or
maybe had to move to a larger disk system when we moved up from Mini Unix.
The details have gotten hazy.)
19 Dec
19 Dec
6:25 a.m.
New subject: IBM 2315 Cartridges
I have such a drive connected to an 11/45. It's branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
physically like an RK05 pack) and present as 4 RK05 drives to the
controller - two on the fixed platter and two on the removable one. Haven't
had the time to try and get them to work yet, but such a device does exist.
On Thu, Dec 18, 2025 at 7:16 PM brian--- via cctalk <cctalk(a)classiccmp.org>
wrote:
No. The only
DEC drive that had removable plus fixed on the same spindle
was the RC25.
If I remember correctly it was Diablo that sold an RK05-compatible drive
with one fixed platter and one removable cartridge. I encountered it on a
PDP 11/34 running Mini Unix and then, hmmm, Unix v<something small>. (Or
maybe had to move to a larger disk system when we moved up from Mini Unix.
The details have gotten hazy.)
20 Dec
20 Dec
6:29 a.m.
New subject: IBM 2315 Cartridges
On Fri, Dec 19, 2025 at 12:25 AM Nadav Eiron via cctalk
<cctalk(a)classiccmp.org> wrote:
I have such a drive connected to an 11/45. It's
branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
physically like an RK05 pack) and present as 4 RK05 drives to the
controller - two on the fixed platter and two on the removable one. Haven't
had the time to try and get them to work yet, but such a device does exist.
Sounds like PM-DD/8 drives.
Connor gave me a set of four 33xx/34xx Plessey drives this year along
with a Formatter box and some cables that happen to have DEC backplane
ends but they 100% need to be deep-cleaned (gloves and respirator ;-)
before anything. I've looked at some of the docs on Bitsaves and they
appear to spin faster than DEC RK05s (2400 RPM vs 1500 RPM) and have a
similar but extended interface (mostly extra address bits) for
capacities several times that of an RK05. IIRC there are models in
this series with anywhere from just the removable platter to a
removable platter plus up to 3 fixed platters.
It does seem that the disks spin too fast to connect up to an
unmodified DEC controller even if one ignores the extra address bits
and treats it like an RK05-F. I have not investigated what's in the
Formatter enclosure except to see a large number of 14 and 16-pin DIP
ICs.
The drives appear to have an electrically similar termination scheme
as RK05 drives, but not mechanically the same and with a few more
signals (for the extra address and status/error bits).
I also got a tub of packs with the drives. Presuming they are safe to
mount, they could be interesting to image. Dates on the labels are
mostly 1980-81
-ethan
6:35 a.m.
New subject: IBM 2315 Cartridges
On Sat, Dec 20, 2025 at 12:29 AM Ethan Dicks <ethan.dicks(a)gmail.com> wrote:
Connor gave me a set of four 33xx/34xx Plessey drives
this year along
with a Formatter box...
Pertec, not Plessey. My mistake.
http://www.bitsavers.org/pdf/pertec/hardDisk/108116_D3400_Dual_and_Quad-Dis…
Given the sad condition from previous long-term storage, perhaps the
best/cleanest of the four might be made operational again, but
probably two of them are beyond reasonable measures.
-ethan
7:08 a.m.
New subject: IBM 2315 Cartridges
On Sat, Dec 20, 2025 at 12:35 AM Ethan Dicks <ethan.dicks(a)gmail.com> wrote:
On Sat, Dec 20, 2025 at 12:29 AM Ethan Dicks
<ethan.dicks(a)gmail.com> wrote:
I just did a slightly deeper dive on the docs on Bitsavers and learned
that the lone D3341 is a 1500 RPM device (xxx1) and has one fixed
platter (100 or 200 tpi) in addition to the removable 2315 cartridge
(at 100tpi). For reference, the RK05-J is 100 tpi @ 1500 RPM and the
RK05_F is 200 tpi @ 1500 RPM. Unfortunately, this D3341 is also
marked "SSC" for "Special [Interface] Special Configuration" - which
the manual says specifically "not described in this manual", and is
marked "Spec. Interface SC908", which is how one would select the
correct documentation. If anyone happens across some D3xx1 drives, if
the extended model number ends with "-Cxx" (especially "-CWU"), the
"C" is for "Electrically _C_ompatible with Diablo Model 30".
The other three drives are model D3482 which appears to indicate 2400
RPM (xxx2). With three fixed platters and one 2315 cartridge (xx8x).
All four drives use hard-sector 12-sector media (same as RK05 on
PDP-11). All the media is 2200 bpi so it suggests that the tub of
2315 cartridges could be popped into an RK05-J and imaged. I would
_definitely_ want to clean any of these before mounting in a working
drive.
Given what I've just uncovered, perhaps I have a pile of strange
hardware that's going to be difficult to talk to, and a tub of 2315
cartridges which might be perfectly fine in an RK05-J on an RK11
controller of some kind (RK11-C, RK11-D, RKV11-D...)
-ethan
Connor gave me a set of four 33xx/34xx Plessey
drives this year along
with a Formatter box...
Pertec, not Plessey. My mistake.
http://www.bitsavers.org/pdf/pertec/hardDisk/108116_D3400_Dual_and_Quad-Dis…
22 Dec
22 Dec
9:48 a.m.
New subject: IBM 2315 Cartridges
On Thu, 18 Dec 2025, Nadav Eiron wrote:
I have such a drive connected to an 11/45. It's
branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
We have a couple of those, all branded as Plessey, but they are Wangco
type F drives. They have one fixed and one removable platter.
It is like two RK05, not RK05F.
physically like an RK05 pack) and present as 4 RK05
drives to the
controller - two on the fixed platter and two on the removable one. Haven't
This would be on the PDP-8 / RK8E where each platter is divided into two
parts because OS/8 can't handle as many blocks as one entire platter has.
This makes your 4 logical drives, but it is still only like two RK05
drives.
Christian
10:01 a.m.
New subject: IBM 2315 Cartridges
Sorry, It's been a long time, I forgot about the sector slots in the hub
ring.
Jim
On Mon, Dec 22, 2025 at 12:48 AM Christian Corti via cctalk <
cctalk(a)classiccmp.org> wrote:
On Thu, 18 Dec 2025, Nadav Eiron wrote:
I have such a drive connected to an 11/45.
It's branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
We have a couple of those, all branded as Plessey, but they are Wangco
type F drives. They have one fixed and one removable platter.
It is like two RK05, not RK05F.
physically like an RK05 pack) and present as 4
RK05 drives to the
controller - two on the fixed platter and two on the removable one.
Haven't
This would be on the PDP-8 / RK8E where each platter is divided into two
parts because OS/8 can't handle as many blocks as one entire platter has.
This makes your 4 logical drives, but it is still only like two RK05
drives.
Christian
4:43 p.m.
New subject: IBM 2315 Cartridges
Nope. Those are different drives. Mine has 2 *physical* RK05 drive IDs
for each platter. Look at (PDF) pages 12-13 in this file:
http://www.bitsavers.org/pdf/plessey/peripheral/Plessey_Minicomputer_Add-On…
I believe you're describing the PM-DD/11B and I have the PM-DD/11C. I have
them on a PDP-11/45, so OS/8 isn't part of the equation :)
Nadav
On Mon, Dec 22, 2025 at 12:48 AM Christian Corti via cctalk <
cctalk(a)classiccmp.org> wrote:
On Thu, 18 Dec 2025, Nadav Eiron wrote:
I have such a drive connected to an 11/45.
It's branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
We have a couple of those, all branded as Plessey, but they are Wangco
type F drives. They have one fixed and one removable platter.
It is like two RK05, not RK05F.
physically like an RK05 pack) and present as 4
RK05 drives to the
controller - two on the fixed platter and two on the removable one.
Haven't
This would be on the PDP-8 / RK8E where each platter is divided into two
parts because OS/8 can't handle as many blocks as one entire platter has.
This makes your 4 logical drives, but it is still only like two RK05
drives.
Christian
5:44 p.m.
New subject: IBM 2315 Cartridges
I used DEC for years, from straight -8 and the11/45 at OMSI west lab, to
Metheus BSD 4.1/4.2, Sys V and RT-11 to the 90's with microvax, Those were
the days when it actually felt like you helping humanity, making life
better. Not any more.
On Mon, Dec 22, 2025 at 7:43 AM Nadav Eiron via cctalk <
cctalk(a)classiccmp.org> wrote:
Nope. Those are different drives. Mine has 2
*physical* RK05 drive IDs
for each platter. Look at (PDF) pages 12-13 in this file:
http://www.bitsavers.org/pdf/plessey/peripheral/Plessey_Minicomputer_Add-On…
I believe you're describing the PM-DD/11B and I have the PM-DD/11C. I have
them on a PDP-11/45, so OS/8 isn't part of the equation :)
Nadav
On Mon, Dec 22, 2025 at 12:48 AM Christian Corti via cctalk <
cctalk(a)classiccmp.org> wrote:
On Thu, 18 Dec 2025, Nadav Eiron wrote:
I have such a drive connected to an 11/45.
It's branded as Plessey. The
drives are double density RK05 compatible (i.e., it's like an RK05F + a
"removable RK05F" with a specially marked removable pack that looks
We have a couple of those, all branded as Plessey, but they are Wangco
type F drives. They have one fixed and one removable platter.
It is like two RK05, not RK05F.
physically like an RK05 pack) and present as 4
RK05 drives to the
controller - two on the fixed platter and two on the removable one.
Haven't
This would be on the PDP-8 / RK8E where each platter is divided into two
parts because OS/8 can't handle as many blocks as one entire platter has.
This makes your 4 logical drives, but it is still only like two RK05
drives.
Christian
5:52 p.m.
New subject: IBM 2315 Cartridges
Yep After sleeping it off, I think the spindle ring was on RP03/Winchester
style packs, Or maybe I'm hallucinate like chatgpt, Pushing 70 and feeling
it. I can't believe I was running up and down stairs at HP just 8 years
ago. Feels like 100.
On Mon, Dec 22, 2025 at 8:44 AM Jim Davis <jim.p.davis(a)gmail.com> wrote:
I used DEC for years, from straight -8 and the11/45
at OMSI west lab, to
Metheus BSD 4.1/4.2, Sys V and RT-11 to the 90's with microvax, Those were
the days when it actually felt like you helping humanity, making life
better. Not any more.
On Mon, Dec 22, 2025 at 7:43 AM Nadav Eiron via cctalk <
cctalk(a)classiccmp.org> wrote:
Nope. Those are different drives. Mine has 2
*physical* RK05 drive IDs
for each platter. Look at (PDF) pages 12-13 in this file:
http://www.bitsavers.org/pdf/plessey/peripheral/Plessey_Minicomputer_Add-On…
I believe you're describing the PM-DD/11B and I have the PM-DD/11C. I have
them on a PDP-11/45, so OS/8 isn't part of the equation :)
Nadav
On Mon, Dec 22, 2025 at 12:48 AM Christian Corti via cctalk <
cctalk(a)classiccmp.org> wrote:
has.
On Thu, 18 Dec 2025, Nadav Eiron wrote:
> I have such a drive connected to an 11/45. It's branded as Plessey.
The
> drives are double density RK05 compatible
(i.e., it's like an RK05F +
a
"removable RK05F" with a specially marked removable pack that looks
We have a couple of those, all branded as Plessey, but they are Wangco
type F drives. They have one fixed and one removable platter.
It is like two RK05, not RK05F.
physically like an RK05 pack) and present as 4
RK05 drives to the
controller - two on the fixed platter and two on the removable one.
Haven't
This would be on the PDP-8 / RK8E where each platter is divided into two
parts because OS/8 can't handle as many blocks as one entire platter
This makes your 4 logical drives, but it is still
only like two RK05
drives.
Christian
23 Dec
23 Dec
10:13 a.m.
New subject: IBM 2315 Cartridges
On Mon, 22 Dec 2025, Christian Corti wrote:
Nope. Those are different drives. Mine has 2
*physical* RK05 drive IDs
for each platter. Look at (PDF) pages 12-13 in this file:
http://www.bitsavers.org/pdf/plessey/peripheral/Plessey_Minicomputer_Add-On…
Uh, well, you are describing the top loader drive that uses IBM 5440
style cartridges, i.e. physically like the RL01 cartridges. Something
completely different from what we are talking about. This thread is about
2315 type cartridges for front loading drives ;-)
Of course, your drive has twice the capacity of an RK05 drive.
Christian
2:48 p.m.
New subject: IBM 5440 DEC drives (better than 2315 Cartridges)
Hey Christian!
Oh you have one of these too? I thought I was the only person with the
mighty Plessey 4 RK05 disk drive system. I have one drive, the
bulkheads/cables, and of course the weird Plessey controller for it. And
a couple of packs.
This drive system is a Diablo 44 (I think) model with 10mb on a fixed
platter and 10mb on a removable RL01 like cartridge. It's pretty heavy,
top loaded with a front door, I think it pulled out of the cabinet on
rails. The controller mapped each head as an RK05 so you wound up with
DK0 and 1 on the removable platter and DK2 and 3 on the fixed platter.
Mine does not spin up currently (last tried it a few years ago) and if
there are others with this system I'd love to start a thread here or on
the forum. It did work; I used to run RSX11M 3.2 on it and used it as a
multi player gaming system for science fiction conventions in the 1980's.
CZ
On 12/23/25 04:13, Christian Corti via cctalk wrote:
On Mon, 22 Dec 2025, Christian Corti wrote:
Nope. Those are different drives. Mine has 2
*physical* RK05 drive IDs
for each platter. Look at (PDF) pages 12-13 in this file:
http://www.bitsavers.org/pdf/plessey/peripheral/Plessey_Minicomputer_Add-On…
Uh, well, you are describing the top loader drive that uses IBM 5440
style cartridges, i.e. physically like the RL01 cartridges. Something
completely different from what we are talking about. This thread is
about 2315 type cartridges for front loading drives ;-)
Of course, your drive has twice the capacity of an RK05 drive.
Christian 
19 Dec
19 Dec
4:51 p.m.
New subject: IBM 2315 Cartridges
On 12/18/25 21:15, brian--- via cctalk wrote:
Yes, Diablo made a one-fixed, one cartridge drive.
Jon
No. The only
DEC drive that had removable plus fixed on the same spindle
was the RC25.
If I remember correctly it was Diablo that sold an RK05-compatible drive
with one fixed platter and one removable cartridge. I encountered it on a
PDP 11/34 running Mini Unix and then, hmmm, Unix v<something small>. (Or
maybe had to move to a larger disk system when we moved up from Mini Unix.
The details have gotten hazy.)
22 Dec
22 Dec
9:43 a.m.
New subject: IBM 2315 Cartridges
On Fri, 19 Dec 2025, Jon Elson wrote:
On 12/18/25 21:15, brian--- via cctalk wrote:
No. Diablo sold the Series 30 as RK02/RK03. It was a removable-platter
only drive.
Christian
If I remember correctly it was Diablo that sold
an RK05-compatible drive
with one fixed platter and one removable cartridge. I encountered it on a
Yes,
Diablo made a one-fixed, one cartridge drive.
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days inactive
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13 comments
7 participants
participants (7)
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brian＠quarterbyte.com -
Chris Zach -
Christian Corti -
Ethan Dicks -
Jim Davis -
Jon Elson -
Nadav Eiron