RK05 disk drive versions

[Al Kossow]

To my knowledge no hobbyist has built an interface that can perform the sector encode/decode functions of the RK11/RK8
There have been expensive RK disk emulators for decades.

The closest was the FPGA interface board Carl Clauch did for reading Xerox Alto disk packs

I'm skeptical you would be able to do this in real-time with an Arduino

 

[Al Kossow]

That drive seems to be a very old one, there are more differences with later drives...

there were some pretty big changes between the RK05 and RK05J

 

[Al Kossow]

And I still wonder why this extra switch is in the first RK05 drive which I had earlier.
That drive seems to be a very old one, there are more differences with later drives...
View attachment 67115

we have many RK05 pictures from the DEC photo archive CHM now has. I'll see if I can find one with that
switch. I'm going to guess it is a power switch

 

[Roland Huisman]

I'm skeptical you would be able to do this in real-time with an Arduino

I agree. My main goal is to have a test interface to control the drives. But if it is possible to read or write a pack image then this would be awesome I think. The data clockrate is 1.44MHz from the disk pack. I have a 84MHz cpu so very little processing time in between. But if I can just read or write single sectors, then I'm fine for images. It was not my goal to make a drive which you could connect to simh/linux. We will see where it ends... The main problem is spare time as always...

From what you say these may be helpful at some stage (unless you already have them). Head alignment disk and test programs.

Yes I'm pretty sure I will need such an alignment pack... I had some pictures for the next posting waiting... Here they are...

There are serious problems with some of the linear positioning sensors. The glue from the
sensor element and the bulb is aged and comes off from the metal and moves... So the sensor
gets misaligned. See pictures...



Then something about the sensor bulbs... These are aging too. Some just go open circuit, others are getting dark
and the light output decreases. With low light output the linear sensor can skip cylinders cause seek errors.



These bulbs are something special too. These have a straight filament. This filament is
placed inline with the lines of the linear sensor.



I have done a lot of searching to find compatible bulbs. But this was impossible.
The original bulb has a C8L filament construction. The best alternative which I
could find was a CC-6 bulb having a straight filament and the right voltage and current.

I found the bulbs in the US. Jack Rubin helped me to get them in the Netherlands.
The bulbs were not on stock and I had to wait a while for them. So Thanks Jack!



So when replacing the bulbs with the other filament, you have to rotate the bulb pcb for 90 degrees.
All drives are now running smoothly, go to RDY and ON CYL. So now I can check the rest of the calibrations...



"ON CYL" just means that the drive goes to cylinder 0. This does not say anything about the alignment.
The cylinder 0 is just obtained from the information of the linear positioning sensor. Aligning the heads
will make sure you are on cylinder 0.

So yes I need this pack indeed...



On the other hand, if you are using packs which are formatted in just one drive you don't need alignment.
but your packs will not be readable in another drive...

Regards, Roland

 

[ftcnet]

... I don't think there is any relevant differences between the drives. I wonder if the ability to run 8 drives on a controller requires the updated cards, possible. Old style addressing have four pins. One for each drive. So a max of 4 drives on the controller. There are variants of controllers which select drives with a binary encoding on these pins instead, and allowed for 8 drives.

There may be some interest in the RKS8-E M7107 scan I just uploaded.

 

[Roland Huisman]

The summer is coming to an end, so it is time for hobby again. One of the worst and incomplete RK05 drives is back online. Positioner lamp replaced, sensor glued back together, new blower bearings, new air duct foam, new front lamps, reused power supply because that was missing. Drive was originally meant to scrap, but it is alive and kicking again.

Little bit experimenting, trying to make the pack bootable. Try again tomorrow... I think I missed a step.

 

[Roland Huisman]

Okay, something strange happened. I can't boot from the RK05 from within a running RT11 5.4B.
But when I just use the M9312 RK05 bootstrap it works like a charm! So I've written a
few more RT11 bootable packs.

Does anyone know of a RK05 disk image with fun games on it? Would love to run Tetris for example :grin:
DECtape or other media is fun too off course.

Regards, Roland

 

[BitWiz]

Roland,

Did you ever finish your RK05 exerciser?

MIke

 

[Roland Huisman]

Hi Mike, Well most of my projects are standing still at the moment since I changed to another job at a school nearby. I'm quite busy and I hope to have a bit more time in the next school year. It is just software what I have to do since the hardware seems to be okay.

I have my spare rk05 drive waiting underneat my desk to do the tests. (I have more drives than rack space )

But the tester is still on my todo list. I have a few bare spare boards for people who want to experiment with a tester in the future.

Regards, Roland

 

[BitWiz]

Roland,

Congrats on the new job. I have one RK05 in pieces with bad bearing on the head positioner and fan and another that I think might work but needs some TLC. I need to get my 8/E up and running and stable before I really tackle the RK05.

I don't know how i can help you with the software but let me know if there is something i can do to help.

Mike

 

[PDP11GY]

Hello, everyone,
I'm in the process of developing a RK05 emulator together with a RX01/RX02 emulator in addition to my projects
based on the DE10-Nano FPGA board. My problem is the design of a PCB board and I can't
find any manufacturer that offers a plug-in interface. Must be the same size as one slot
in the RK05 backblane. In this thread, roland has already presented his RK05 test interface.
This test interface seems to have the correct connector. Where can I order this connector from?
One final general question. Is there even a need for an RK05 emulator?
Thanks, Reinhard

 

[vrs42]

This test interface seems to have the correct connector. Where can I order this connector from?
One final general question. Is there even a need for an RK05 emulator?

Is this the female edge connector that takes a flip-chip card? If so, folks are ordering a similar connector from a fellow who's special ordered them and is selling the extras to fellow hobbyists.

As for the need for RK05 emulation, I'd say yes, mostly because the state of RL01/RL02 support for PDP-8 is sort of barely there, and Omnibus 8/E and 8/A controllers and software for the RK05 are out there. Keeping the rust rotating is a maintenance headache that may not be sustainable forever, and there are probably already plenty of folks not up to restoring a real drive.

Vince

 

[BitWiz]

Count me in for the emulator.

I have a few "over the top" edge connectors available from my purchase, please direct message me if you are interested.


This is the connector:

 

[thunter0512]

As for the need for RK05 emulation, I'd say yes, mostly because the state of RL01/RL02 support for PDP-8 is sort of barely there, and Omnibus 8/E and 8/A controllers and software for the RK05 are out there. Keeping the rust rotating is a maintenance headache that may not be sustainable forever, and there are probably already plenty of folks not up to restoring a real drive.

I like the phrase ""keeping the rust rotating".

I too would be very interested in a RK05 emulator hooked up to an Omnibus controller board set.

 

[Roland Huisman]

Hello, everyone, I'm in the process of developing a RK05 emulator together with a RX01/RX02 emulator in addition to my projects based on the DE10-Nano FPGA board. My problem is the design of a PCB board and I can't find any manufacturer that offers a plug-in interface. Must be the same size as one slot in the RK05 backblane. In this thread, roland has already presented his RK05 test interface. This test interface seems to have the correct connector. Where can I order this connector from? One final general question. Is there even a need for an RK05 emulator? Thanks, Reinhard

Hi Reinhard! Good to hear from you!

A FPGA RK05 disk emulator would be great. I have an official one (VRC 8256) from the nineties I think...

https://forum.vcfed.org/index.php?threads/rk05-emulator-vermont-research-corporation-vrc-8256-documentation-wanted.1227091/

But I would love to have a FPGA version too. My VRC 8256 is configured as a 12 sector emulator for the PDP11. I have no idea how to set it to use it on a PDP8 with 16 sectors. It should be possible, but I don't have documentation.

I have your RL01/02 interface still waiting for me to buy a DE10-nano. My 11/34 is now up and running again, so testing the RL11 controller would be the next step. The delivery time on mouser for the DE10-nano is 127 weeks at the moment. But buying directly trough Terasic might be an option. Unfortunately a DE10-nano is quite expensive to get here at the moment...

About the connector.... Why don't you take the easy way... Let someone find their own H851 blocks and let them use the BC11 cable as I do here with my test card:



For the PDP8 RK8E controller you don't even need the BC11 cable. The cable is a M993 and has 40 pin IDC connectors at the RK8E side. So you can use these as well.


So in my opinion you could just use an edge connector and the IDC connectors. And if someone has only a RK11 controller, it might even be possible to plug the emulator directly into the controller instead of the BC11 cable... (I would add a few resistor arrays as option to terminate the bus...) And if you have a real drive you can also plug in the emulator as a bus terminator in the last RK05 drive...

The last time I was only testing RK11 controller boards to see which is working and which are broken. I prefer to use the emulator as well instead of spinning up and head loading a real RK05 drive... I have 6 board sets to fix... It is not a good idea to go fault finding in these controller boards with a working real RK05 on it...


Regards, Roland

 

[PDP11GY]

My idea how to implement the RK05 emulator: disconnect the real RK05 ( remove the BC11 cable )
and replace it with the -RK05-emulator. Roland , thank you for your suggestions, I'll think about it.
In general, however, the main problem at the moment is the availability of FPGA boards/chips.
Times change very quickly. Meanwhile, SIMH is already running with RT11 on a Raspberry PI Pico.
I've already considered other cheaper FPGA boards like the Tang Nano 9k. Unfortunately from
China and doesn't work quite as it should. The US board Mercuri 2 would be useful, but is it too
expensive? So I'm sticking with the DE10-Nano board for now.
It's probably better to open a new thread "DEC disk emulators" to keep track and not develop
everything twice and exchange experiences and advice.
All best for 2023. Reagrds, Reinhard

 

[Roland Huisman]

Hi Reinhard,

My idea how to implement the RK05 emulator: disconnect the real RK05 ( remove the BC11 cable ) and replace it with the -RK05-emulator.

Well it is your project off course, but I would like to expand my PDP11/20 for example. I have two working RK05 drives on this machine, and I'm not going to disconnect these. To run the smallest Unix on it you need at least three RK05 drives. One spare drive is waiting under my desk. That drive works too, but I don't have any rack space left. In that case I would love to expand the amount of real drives with emulated drives. Check my PDP11/20 here, then you see what I mean... (These are the restored RK05 drives from this topic by the way!)

The UniBone can emulate a RK11 controller and RK05 disks, but is not able to expand the existing amount of real drives. Maybe I can change the address of the emulated controller so I have two controllers, a real one and an emulated one. But I'm not sure how that will play out. For now I'm using an emulated RL11 with RL02 disk images and a real RK11 controller with real RK05 drives.

Here you can see the PDP11/55 from forum member geerol58, he used one working RK05 drive and uses a VRC 8256 to emulate the other two RK05 drives. He demonstrates Unix v7m on it.

Roland , thank you for your suggestions, I'll think about it. In general, however, the main problem at the moment is the availability of FPGA boards/chips. Times change very quickly. Meanwhile, SIMH is already running with RT11 on a Raspberry PI Pico. I've already considered other cheaper FPGA boards like the Tang Nano 9k. Unfortunately from China and doesn't work quite as it should. The US board Mercuri 2 would be useful, but is it too expensive? So I'm sticking with the DE10-Nano board for now. It's probably better to open a new thread "DEC disk emulators" to keep track and not develop everything twice and exchange experiences and advice. All best for 2023. Reagrds, Reinhard

How about the BeagleBone Black? Farnell has about 15000 on stock... The complete UniBone runs on it. That includes emulated RK05 controller and emulated RK05 disks. I wonder if the BeagleBone and this UniBone code could be useful to just make just a disk emulator? Maybe Joerg can tell something about it...

Regards, Roland

 

[GreyHairedDECfan]

You folks truly amaze me. I don't have the smarts, time, or patience to do what you all are doing. But it's truly great to see so much interest in Digital gear including the people who've recreated (nearly) original hardware using modern-day components.

Me, I'm happy just to fire up RT-11 or RSTS (though I'd love RSX which I used for a number of years... I have a 3.2DM disk but it seems to be a very minimal build and I can't do much of anything with it) on simh and enjoy without having to worry about smoking capacitors and other maladies of the original gear. That's about the limit of what I can do these days.

My hat is off to you. Happy New Year!

 

[PDP11GY]

Roland, thanks again for your information.
Seems to be a difference connecting a PDP-11 or a PDP-8 to a RK05.
People always point me to joerg's Unibone. But this is a completely different application.
In my understanding, a disk emulator as a 1:1 replacement of the hard disks. Maybe we should
first clarify the term "emulator". A real RK05 emulator must reconstruct the disk timing 1:1
and must be able to read the data from the disk without any pdp-host. This is my goal and is
implemented in the RL01/02 and MFM disk emulator. BeagleBone Black is useless for my purpose and
unfortunately also outdated. Meanwhile, most can be realized by a Raspberry PI PICO, like:
https://github.com/Isysxp/Pico_1140 . The project has been expanded and now has a serial
output. So you put a PICO in a Vt100, run PDP11/40 emulator with RK05 RT-11.

pdp11/40 Emulation auf dem Raspberry Pi Pico - VzEkC e. V.

Ueber die Seite zur Emulation der pdp11/40 auf dem Raspberry Pi Pico bin ich vor kurzem "gestolpert" bei der Suche nach weiteren moeglichen Emulationen fuer den Kleinen Da es kein Arduino-IDE Code ist, musste wieder meine Pico/SDK Installation herhalten,…

forum.classic-computing.de

I will try to realize a RK05 emulator version based on Raspberry PI PICO and a Tang Nano 9k FPGA.
I will be happy to inform you further. Regards, Reinhard

 

[Roland Huisman]

Hi Reinhard,

Sounds great to me with a Pi pico and the Tang Nano 9k FPGA! I know the real drives have to be timed and the serial data is clocked at 1.4MHz. I'm not familiar with the exact possibilities from the BBB. I just tried to think with you and I really hope you can make a successful disk emulator.

Regards, Roland