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Unusual RL disk packs

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
Just wondering if anyone can help me identify an RL disk cartridge please.

The cartridges are marked "Control Data 848-12".

When I try to LOAD these on a known good RL01 system (QBUS with RLV12 controller), the drive just makes a clicking sound about once per second. The READY light never comes on. I've tried 3 of the 25 cartridges. Same result each time.

These are physically the same form factor as a DEC RL cartridge, but blue in colour.

The outer box has handwriting saying "5MB/12S".

Any ideas what these could be for? Does an RL01 system on a PDP-8 use the same cartridges as a PDP-11?

Control Data 848-12 Cartridge.jpg
 

Terry Kennedy

Experienced Member
Joined
Jul 7, 2017
Messages
241
Location
New York
Just wondering if anyone can help me identify an RL disk cartridge please.
It isn't an RL0x cartridge.

These are physically the same form factor as a DEC RL cartridge, but blue in colour.

The outer box has handwriting saying "5MB/12S".

Any ideas what these could be for? Does an RL01 system on a PDP-8 use the same cartridges as a PDP-11?
The physical media is 5440, as that is the underlying IBM model number for that format. It was adopted by many minicomputer manufacturers due to inexpensive drives such as the Diablo 44 and easy to build controllers (for the time!). But there were a huge number of variants which were incompatible. The packs had varying numbers of hard sector markers and not all system manufacturers allowed you to format your own packs, even if they were physically compatible.
 

Mal

Experienced Member
Joined
Apr 3, 2008
Messages
91
Terry - thanks for the explanation.

Is anyone interested in these 25+ cartridges (or some of them)?

Free of charge (you just pay for packing and shipping). These are in Melbourne, Australia.

I'd drop them at my local "Pack and Send" store, for you to arrange packaging and shipping. They will ship international, but that likely to be very expensive.

They are currently stored in single-wall cardboard boxes - 4 cartridges per box.

If no interest, they'll go to e-waste in a couple of weeks.

Malcolm.
 

Lou - N2MIY

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Joined
Apr 1, 2008
Messages
1,306
Location
Albuquerque NM / Potomac MD
I have wondered if an RK05 can be re-packed with the platter from an RL01. If so, these packs should not be sent to the scrapper. I have only two good RK05 packs, but three crashed packs. I have saved the crashed packs with the thought that maybe they could be repacked. Since the RK05 drive can format packs, it doesn't matter how the original platter was formatted (and yes, as we know, RL packs are factory formatted and not field re-formattable [unless I build a formatting lathe someday with a precision lead screw head positioner.])

Lou
 

NF6X

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Joined
Sep 9, 2013
Messages
1,534
Location
Riverside, CA, USA
Speaking of formatting RL packs, one thing that I've wondered about is whether the interleaved servo bursts have the same radial width as the data tracks. If they have the same width, then it seems to me that it would be possible to heavily modify an RL02 drive to make it into an RL02 pack servo writer. But if the servo bursts need to be physically wider to span adjacent tracks properly, then a servo writer would need special heads with the proper magnetic gap width. I can envision what would be needed to modify a drive's head positioner system to be able to work as a servo writer,[SUP]*[/SUP] but I haven't a clue about how to pursue fabricating heads.

The drives in my collection which use 5440 style packs include some RL02 drives, and the 6045 drive in my DG Nova 3 system (one removable platter and one fixed one). The 6045 drive includes an optical position sensor in the head positioner, so I think that implies that it could format a bulk-erased platter? The RL02 drives require packs with pre-recorded servo bursts for positioning; does that imply that there's no need for a careful alignment to be performed after replacing heads in the RL02 drives? I haven't gotten deep enough into either kind of drive yet to know the answers to those assumptions for certain.



* Either replacing the positioner with a leadscrew as Lou suggested, or adding a high resolution encoder to the positioner. Either case would involve all new electronics to drive the positioner and to write the servo bursts.
 

MattisLind

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Joined
Sep 30, 2013
Messages
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Location
Stockholm, Sweden
Lou, tried to send you a PM, but your inbox is full? If you want some RK05 packs you can have them for cost of shipping. 12 or 16 sector?
 

Terry Kennedy

Experienced Member
Joined
Jul 7, 2017
Messages
241
Location
New York
Speaking of formatting RL packs, one thing that I've wondered about is whether the interleaved servo bursts have the same radial width as the data tracks. If they have the same width, then it seems to me that it would be possible to heavily modify an RL02 drive to make it into an RL02 pack servo writer. But if the servo bursts need to be physically wider to span adjacent tracks properly, then a servo writer would need special heads with the proper magnetic gap width.
Someone with a crashed pack (or unusable for some other reason) and some Magnasee should be able to give you an idea - 5440 technology was 100TPI and should be visible. I think the RL02 was just a 200TPI version of the same drive guts.

The drives in my collection which use 5440 style packs include some RL02 drives, and the 6045 drive in my DG Nova 3 system (one removable platter and one fixed one). The 6045 drive includes an optical position sensor in the head positioner, so I think that implies that it could format a bulk-erased platter?
The 6045 is the DG-built replacement for the re-branded Diablo 44, DG model 4234. RDOS treats them identically (SYSGEN question "Top loaders?") and they are the same device ID for bootstrap purposes (100033, Program Load). It is probably possible to infer which model you're talking to - the source for HIPBOOT (the "new generation" RDOS bootstrap from 1978 or so) will probably show you if it is possible or not. Packs physically compatible with the 4234 (correct number of sectors*) were formattable with a diagnostic utility.

Those were the days when you'd recover from a head crash by wiping out the inside of the drive with paper towels soaked in (a now-banned) cleaning fluid, then change the heads and do a fly-by-night alignment with a regular data pack and a 'scope - when you see bits, you know you're on the outermost track. Adjust for best amplitude and button it up.

I expect that the 5-over-5 removable/fixed design was responsible for more data loss due to operator error than anything else of that era. To back up the disk, you needed 2 scratch cartridges, and then the dance went like this:

o Put the scratch pack in the top. Copy the bottom (fixed) to the top.
o Remove the scratch pack and insert the production top pack. Copy the top to the bottom.
o Remove the production pack and put the second scratch pack in the top. Copy the bottom to the top.
o Remove the second scratch pack and put the first scratch pack in. Copy the top to the bottom.
o Remove the first scratch pack and reinstall the production pack.
o Try booting and see if you made any mistakes...

The RL02 drives require packs with pre-recorded servo bursts for positioning; does that imply that there's no need for a careful alignment to be performed after replacing heads in the RL02 drives? I haven't gotten deep enough into either kind of drive yet to know the answers to those assumptions for certain.
If they're using industry-standard 5440 sliders (even with custom heads), there is enough "slop" in the head alignment slot that you can adjust them off the usable area of the media. Plus, if you have the top and bottom heads unaligned, changing surfaces is going to take as long (or longer) than a 1-cylinder seek on the same surface.

* My first experience with buying 3rd-party 4234 disk packs (from Minicomputer Accessories - later INMAC [INternational Minicomputer Accessories Corporation]) didn't go well. I apparently got some hippie stoners (said my up-tight 18-year-old self) - they answered the phone "Customer serrrrrrvvvvvviiiiiccccee. Can I ... help? ... you?" They shipped replacements which were the same wrong ones that they originally shipped - took a few iterations to get the right packs.
 

Doug G

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Joined
Jun 16, 2012
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SoCal
Maybe these packs were for CDC Hawk disk drives, my memory says those disk drives used a similar-looking top loading removeable cartridge. Back in the 1970's I used to service a DG Nova2 system with a System Industries disk controller and free-standing CDC Hawk drive, the only Hawk we covered in a world full of CDC SMD drive.. Our group at CDC serviced SMD drives, but I don't recall running across many, if any, Hawks hooked to DEC systems.
 

PG31

Experienced Member
Joined
May 31, 2011
Messages
494
Location
Sefton, Meresyside, England
It also looks similar to the CDC 9448 (Pheonix?) drive cartridge. I had a customer in the late 80s - early 90's with these drives connected to PDP-11/73's via an Emulex or Webster SMD I/F.
 
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