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Thread: PDP-11/23+ Restoration Blog

  1. #11
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    Default Nice 11/23+

    Quote Originally Posted by stephenbuck View Post
    Thanks gslick,

    Good point about being period-correct - that's just the kind of info I need!

    I plan on restoring the RL02 drives, but might actually run the museum display off a Raspberry Pi running a disk emulator of some sort to prevent wear and tear on the drives. I know the standard 11/23 configuration included two RL02 drives, but do you know if it was common to use just one RL02 (probably in conjuction with a floppy)?

    The eBay purchase I made included some RD52 drives and, if I remember correctly, an RQDX controller, so I could use that.

    Actually, one reason to use the SMD drives might be to take up space in the rack as blank (or any other type) panels are really hard to find.

    Thanks,
    Steve
    Steve,
    That’s a nice looking system! I’d vote for running RSX11M on it. If you do get an 11/73 sometime then upgrade to M+ to use the I/D capabilities. Actually, M+ will run on the 11/23 but would be tight on the RL02 system disk. If you use the SMD drives that would work.

    The first PDP-11 system I had was a PDP-11/24 with two RL02s, and a DZ11. I ran my first RSX11M SYSGEN from the 5 disk RL02 distribution for RSX11M V4 when I got it. RSX could run from one disk with the second for files. A disk to disk backup of the System disk was easy but you had to boot the memory resident BRUSYS to do a disk backup of the data disk. I think we kept a copy of it on the data disk to make it bootable. The CPU cost $15K, the RL02 $3K each, the DZ11 $3K and floating point in microcode was $600. The F77 compiler was $6700 and required a FPP. We had a number of analytical instruments connected to it as well as a VT125 graphics terminal and HP plotter. We also ran DECnet on the second SLU port that is sometimes used for a TU58 to connect to the 11/44 in the corporate I.T. group.

    Best,
    Mark

  2. #12
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    Default

    Quote Originally Posted by stephenbuck View Post
    I know the standard 11/23 configuration included two RL02 drives, but do you know if it was common to use just one RL02 (probably in conjuction with a floppy)?
    FWIW, I don't recall ever seeing an 11/23 system that mixed RL02 and floppies. Perhaps because of the size mismatch (can't easily back up your RL02 on floppies). And if you (a customer) already has the RL controller and one drive, you might as well just add the 2nd drive (already supported), instead of needing to add another controller card.
    But I could be wrong...

    Pete

  3. #13
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    Quote Originally Posted by saipan59 View Post
    FWIW, I don't recall ever seeing an 11/23 system that mixed RL02 and floppies. Perhaps because of the size mismatch (can't easily back up your RL02 on floppies). And if you (a customer) already has the RL controller and one drive, you might as well just add the 2nd drive (already supported), instead of needing to add another controller card.
    But I could be wrong...

    Pete
    Pete,
    What you suggest above is what we ended up doing (back in 1982). A 3rd RL02 made backups of data disks much easier, it also added another 10 MB of user data file space. But we also added an RX02 to the system to provide an easier way to install small software packages or installs. The RX02 was basically an easy way to move some files. If it was formatted RT-11, it provided a way to move files between RT-11 and RSX. RT-11 did have a DECnet option but it does seem to be one of the "Lost Files" of DEC that many of us would LOVE to find!!

    Best,
    Mark

  4. #14
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    Default

    Everyone will probably get pissed about this but I think the RL family of drives is one of the best series of devices ever built. Ok, so you cannot format them in the field but the basic design is pure simplicity. The servo system that’s just about as simple as any VCR the ability to stack and set the address with the light caps and most important the sealed re-circulating air system unlike the older RK family of drives. And what other drives can you mix and match without any issues, you can run two or three RL-01 drives, a couple RL-02 drives or mix RL-01 and 02 drives and they just work.
    Up until recently you were able to pick up disk packs for next to nothing and I know that it was not uncommon to find things like the XXPD diagnostics packs.
    Installation is simple, alignment only requires a dual trace scope and when working with RT-11 or RSX-11 the five or ten Meg size is not a serious issue.
    As always you can do what you want with your restoration work but if it were me there would be no question of doing a dual drive RL 11/23 system running RT-11
    I currently have a 11/23 running RT-11 with a RL-02 and a CDC tape drive along with a 11/34 with dual RL drives that I use for copying disk packs and if you were going to go the RL/RT-11 way would be willing to do a RT-11 pack with the RT Utilities along with a copy of DEC Basic for a system disk for you, just send a disk pack and I can copy one for you.
    I have RX-02 and had a RX-01 disk drive but no big fan of them considering finding good media and the fact that the drive motors are always running just make them hard to love, at least for me.
    A link to my 11/23 running RT-11 with a RL-02 as the system drive and the CDC open reel:

    https://www.youtube.com/watch?v=oWnjuLS6jxI

  5. #15
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    I'm with you on the RL02 drives!

    This restoration is for a museum and the RL02s are perfect for showing that generation of storage and just plain old cool!

    My only problem is that I don't have enough of them - I'm actually restoring two more-or-less identical machines and I've only got two RL02 drives. If I can ever find two more I'll set up both systems with dual RL02s.

    I do, however, think that I'll run the day-to-day exhibit with a TU58 emulator running on a Raspberry Pi hidden in the rack just to save wear and tear on the vintage hardware. I can always use the old stuff for special occasions.

    I'll be bringing up the RLO2s in the next part of my blog, so wish me luck!
    Last edited by stephenbuck; March 25th, 2020 at 08:58 AM.

  6. #16
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    The RL Drives chug along at 2400 RPM so they don’t live a hard life and unless someone dose something stupid like pull the power while its running they are fairly bullet proof but for a display where it has to stay on for days would think one of the solid state like SD card versions of the drive would be the trick.
    Almost would think that the best choice for such a system would be the 23 being they are the most common and cheapest, if you went with something like a KDF-11 (8186) card they are about the most common and cheapest PDP-11 CPU.
    If you did RT-11 with DEC Basic you can then run something like the basic version of “Lunar Lander” and that would be fun, not as much fun as if you had like an 11/05 graphics terminal version but the Basic version I have on my 11/34 is simple and fun to play with, I just used the code from the Atari Basic Game book and it took little modification.

  7. #17
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  8. #18
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    Default

    Quote Originally Posted by Qbus View Post
    The RL Drives chug along at 2400 RPM so they don’t live a hard life and unless someone dose something stupid like pull the power while its running they are fairly bullet proof but for a display where it has to stay on for days would think one of the solid state like SD card versions of the drive would be the trick.
    Almost would think that the best choice for such a system would be the 23 being they are the most common and cheapest, if you went with something like a KDF-11 (8186) card they are about the most common and cheapest PDP-11 CPU.
    If you did RT-11 with DEC Basic you can then run something like the basic version of “Lunar Lander” and that would be fun, not as much fun as if you had like an 11/05 graphics terminal version but the Basic version I have on my 11/34 is simple and fun to play with, I just used the code from the Atari Basic Game book and it took little modification.
    Qbus,
    First, I love your YouTube video demoing the CDC tape drive! I was unfamiliar with that CDC drive but it looks like a great one to try to find.

    Second, I totally agree with your assessment of how rugged RL02s are. I described earlier the PDP-11/24 system I managed many years ago. Eventually it grew with a combination of hand-me-downs from corporate I.T. and used equipment to eventually fill out seven 19 inch racks.

    PDP-1144a.jpg

    Between the 11/44, two RK07s, three RL02s and TS-11, it was pretty noisy. Anyway one day I was changing an RL02 disk pack and as you can see there are two side by side that were to the left of the 44. I spun the disk down then turned to do something on the console and when I turned around I was in front of the RL02 that was still spinning. When I tried to open the hatch, I should have been stopped by the the doors interlock, but it had failed. It allowed me to open the hatch, then I removed the lid and lifted the handle an attempted to remove the spinning disk. It is hard to describe the awful sound of the heads making very hard contact with the surface. I immediately let go and the noise quit. I spun the disk down and try to figure out what to do next. I really needed the data on that disk, and I figured I already messed up the heads so I didn't have much to loose tp try to spin it up again and see what I could recover. Amazingly BRU was able to copy all the data off that disk. The heads must have scratched an unused part of the disk. After making the copies, I removed the RL02 pack and called DEC field service. All our disk packs were on DEC Maintenance an dI suggested that the tech should come and check out the disk packs. I was listening from the next room when he found the damaged pack and exclaimed wow, this one has a scratch to bare metal. We need to replace this one. I don't remember if he had the replace the RL02 heads or just clean them. At any rate the RL02 is a very solid disk drive as Qbus explained.

    Mark

  9. #19
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    Default

    Here's an interesting question - would love some opinions! Since this restoration is going into a museum and will likely see frequent use, should I rely on the original vintage power supplies or replace them with modern power supplies? I'm worried about fire hazard, hardware damage, etc.
    Last edited by stephenbuck; March 29th, 2020 at 05:20 PM.

  10. #20
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    Quote Originally Posted by stephenbuck View Post
    Here's an interesting question - would love some opinions! Since this restoration is going into a museum and will likely see frequent use, should I rely on the original vintage power supplies or replace them with modern power supplies? I'm worried about fire hazard, hardware damage, etc.
    A couple of ideas:
    - I would imagine that cold power-on is the riskiest thing. Arrange to leave things running, rather than power-cycling. But maybe electricity costs are an issue?
    - Consider implementing an appropriate soft-start mechanism. Would require an understanding of how these supplies work in an under-voltage scenario to decide if it's appropriate at all (these are switching supplies, so undervoltage could actually be a higher stress). But maybe something that ramps up the V over a few 100 mS would be good???
    - Consider adding extra fusing to reduce the possibility of damage if a part goes bad suddenly. For existing fuses, run with the one that is barely big enough. The stock fuses are chosen to NOT blow over a variety of operating conditions, but you are running in a very specific config, so you can narrow the margin considerably.

    Meanwhile, I wonder if your various disk drives are where the real risk is, rather than power supplies... But much of the point in demoing a vintage system is to spin up the storage also.

    Pete

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