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PDP-11/23 and H9276-A

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marmotking

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I have a PDP-11/23 which I thought maybe I could upgrade using an H9276-A backplane. Actually, I have lots of enclosures I could use. Could I use an KDJ11-BF with this backplane and make an 11/23 PLUS? Any help getting started in that direction would be very useful to me. Basically, I guess, I'd like to do something with the H9276-A backplane and a KDJ11-BF or KDJ11-BB or maybe some other processor board that you might think is best. I have other enclosures as well. Does any of this make sense? I'd like to start accumulating parts. I'd really like an 11/23 Plus or better machine if I can construct such things with these parts.
 
That should be a Q22 backplane, so the short answer is "Yes".

Is it in an enclosure with PS?

KDJ11-B will have only a single console serial port, not the two ports of a PDP-11/23+ (which are really nice if you have TU58 emulation in mind) However, it is a faster CPU and could be used to make anything up to a PDP-11/83 - given the correct memory.

To help you proceed, we'll need to know what Q-bus bits and pieces you have on hand.
 
So what I have is an 11/23 complete with power supply, back plane, the original 11/23 CPU board and memory board and for additional parts, I have the Q22 backplane mentioned above and a KDJ11-BF. I don't have any memory that will work with the KDJ11-BF. I'm planning on having to buy those types of parts. I'll have to work my way up to some peripherals. I have an M7555 that maybe could be used for an MFM drive? Qbuses are new and confusing to me, so any guidance in the right direction would be very helpful... Perhaps I could use a MicroVAX SCSI controller?
 
Any idea what kind of RL02 controller I'd need? I have a few of these drives, untested. Perhaps a RLV12?

Could one use a KFQSA DSSI controller? I guess it might depend on what OS one wants to use.
 
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Yep, the RLV12 will work with the RL02 drives. The DSSI controller absolutely will _not_ work with RL02s.
 
Regarding the KDJ11-BF processor and memory: any qbus memory whatever will work with that processor. Although PMI memory (MSV11-J) is desirable for speed reasons, normal QBUS RAM will work with the kdj11 - just remember it goes _below_ the processor in the backplane, not above (which is where PMI RAM wants to be).
 
The M7555 is an RQDX3 controller, and is a handy card to have if you can find a functional MFM drive. The DEC RQDX3 format utility (XXDP ZRQCH0) supports a fairly limited set of hard drives as distributed, but enough detailed information is available here to let you use just about any ST-5xx series MFM hard drive. Depending on the enclosure you're using, you will probably also need either custom cabling or an M9058 distribution card, plus a little bit of external electronics for drive enable / write protect.

The M7555 also supports two floppy drives, possibilities are the RX50, RX33 family, or certain 5.25 inch floppy drives with necessary jumper settings to convince the controller it's a DEC drive.
 
With that potential stable of options, we need to be careful of power supply limits. Consequently, the box becomes focus of our discussion. Please be specific about which you have.

If the Q22 backplane physically fits, it can replace the original if necessary. However it might not be... we also need to identify the original backplane.

If you have the M8186 KDF11-A 11/23 DUAL card, then one of the KDJ11-B M8190 QUAD cards would be preferable. These can be used with "ordinary" QBUS memory (both non-block mode and non-PMI) with a performance penalty. Also note that memory placement is different with PMI memory. (as ROE noted)

I like the MSV11-Q M7551 QUAD memories for these hybrid configurations. Greatest compatibility across CPU types, lowest power requirements, up to 4MB in a single module, and supports Block Mode. PMI MSV11-J M8637 QUAD would be useful only with KDJ11-B boards and is my second choice. Note there are some MSV11-J revisions NOT TO GET with buggy ASICs.

No matter the memory you choose, try to get memory with parity.

RQDX3 M7555 DUAL is a good general choice for MFM QBUS ctl. Also the SCSI ones if you can. The RLV12 M8061 QUAD is preferred to the **RLV11 (M8013, M8014) QUADs for RL01/RL02 applications.

**Note also some of these options require ABCD slots, and some not. Flame and smoke may result in case of error.


  • Any need for 8" floppy? Personally, I'd go DSD rather than original DEC - but it's a pragmatic choice, not a purist one.
  • You need some serial ports. One (KDJ11-B) is not enough and none (KDF11-A) is unusable. I suggest M8043 DLV11-J (aka DLVJ1) 4 line SLU because it can be configured for Console, TU58, plus two more terminals. A DZQ or DHQ will not be useful for TU58 XXDP.
  • Mag Tape?

~

If that were all intended for a single original 11/23 chassis - check the power supply requirements and AC bus loads carefully. I can do one for you, but I expect we'd be uncomfortably close to some limits and over others.
 
Does M7551 require q22/q22 (ab/ab) backplane? Because, H9276-A seems to be all q22/cd (ab/cd) backplane (btw, is this the SAME with those qbus backplanes designed for S-handle cards?)
 
bigral said:
Does M7551 require q22/q22 (ab/ab) backplane? Because, H9276-A seems to be all q22/cd (ab/cd) backplane (btw, is this the SAME with those qbus backplanes designed for S-handle cards?)
Click to expand...
Not quite sure how to respond... let me try this:

Regarding MSV11-Q M7551 Memory cards:

  • I've used M7551 in both Q18 and Q22 backplanes
  • M7551 is Q22 but can be jumpered for Q18 - though I've never known it to be necessary.
  • M7551 can live in ABAB or ABCD slot
  • M7551 is not PMI, and must be in slots after the CPU. (I.E. - CPU in slot 1)
 
marmotking said:
Could one use a KFQSA DSSI controller? I guess it might depend on what OS one wants to use.
Click to expand...

KFQSA is NOT a SCSI controller. The KFQSA is the DSSI controller. They both use 50 conductor ribbon cables but DSSI is not SCSI. I have read that KFQSA / RFxx disks can work on pdp-11 systems but I have not tried this.

RLV11 absolutely cannot be used in an ABAB backplane. However, I have repaired the results of such a tragedy and have documented what was destroyed (and repaired) on alt.sys.pdp11. Just search on RLV11 Successful Repair.

And as a call to all those interested in formatting non-RDxx MFM hard disks on an RQDX3, see this thread by yours truly: http://www.vintage-computer.com/vcf...H0-to-use-any-geometry-MFM-hard-disk-on-RQDX3 which has drawn astoundingly little interest.

Lou
 
I would like to see that document and even try it out perhaps on a PDP-11/03 that I have. I guess I'll need to understand the layout of the backplane among other things. I'll get more information together about the system and post here. I clearly didn't understand enough up front. I will fix that. Also, it seems to me that since power is an issue, it should be easy enough to build a memory board out of modern components and have just a few memory chips on it to give 1MB to 4MB. I'd actually be interested in working this out as a project too. If anyone could help point me to some relevant documents, that would be great. I know there's also been some discussion on a MSCP interface to ATA (either a drive or CF). I don't know if that's gone anywhere, but it could be a way to cut the power requirements as well. I have several DSSI drives, hence the query about using a DSSI controller with a PDP-11 system.
 
Is there any chance one could use an M7622 with a KDJ11-BF? I know that the M7622 is meant for use with a VAX PMI ribbon cable assembly, but given that other Q-Bus style devices have to access the memory too, it seem reasonable that the M7622 is also able to respond to memory cycles off the Q22 bus. I know that an M7622 is 16MB and I can't address that with a KDJ11-BF, so I'd assume that the rest would be wasted.
 
marmotking said:
Is there any chance one could use an M7622 with a KDJ11-BF? I know that the M7622 is meant for use with a VAX PMI ribbon cable assembly, but given that other Q-Bus style devices have to access the memory too, it seem reasonable that the M7622 is also able to respond to memory cycles off the Q22 bus. I know that an M7622 is 16MB and I can't address that with a KDJ11-BF, so I'd assume that the rest would be wasted.
Click to expand...

No, you can only use M7621 MS650-AA and M7622 MS650-BA memory with KA640/650/655/660 CPUs.

While the M7622 MS650-BA is physically plugged into Q-Bus slots, it is not logically directly connected to the Q-Bus. The KA640/650/655/660 CPUs contain a Q22-bus interface (the CQBIC) which implements a scatter-gather map for translating 22-bit Q22-bus addresses into 26-bit main memory addresses. Q22-bus DMA activity does not directly access the MS650 memory. The Q22-bus DMA activity goes through the Q22-bus interface and the memory controller on the CPU to access the MS650 memory.
 
Lou - N2MIY said:
KFQSA is NOT a SCSI controller. The KFQSA is the DSSI controller. They both use 50 conductor ribbon cables but DSSI is not SCSI. I have read that KFQSA / RFxx disks can work on pdp-11 systems but I have not tried this.
Lou
Click to expand...

For most purposes the M7769 KFQSA is just another Q-Bus MSCP controller and should work with any VAX or PDP-11 OS that supports MSCP controllers. I have used a KFQSA in a BA213 with an M7554-SD KDJ11-SD (DECServer 550 CPU but with 11/53 firmware EPROMs) with RSTS/E 10.1 and 2.11BSD.

The only issue is that if you want to reconfigure the KFQSA it really helps to have a VAX CPU you can swap in instead of the PDP-11 CPU so you can do the >>> set host/uqssp/maintenance/service n thing.
 
That's excellent! So I have several DSSI drives in great shape so I went a bought a couple of these boards. I have a microvax for setting up the drives, so no problem. Certainly a lot cheaper than finding a Q-Bus SCSI controller.
 
You can typically get a bare M7769 KFQSA for around $50, example:
http://www.ebay.com/itm/160927479769
So that is cheaper than your typical Q-Bus SCSI controller, if you happen to already have some DSSI drives on hand and the necessary cables and terminators. I have only used original DEC internal DSSI cable sets. Don't know if you can kludge up something using standard 50-conductor ribbon cable, and if you do that then what do you do about termination.

If you want the bulkhead connectors for using external DSSI cables you'll probably end up paying a bit more, example:
$100 - http://www.ebay.com/itm/321317623868 - Feb 07, 2014

If you do have a working DSSI controller configuration you can also add an HSD-05 or HSD-10 converter to SCSI with a BA350 storage shelf. I think you said you have an HSD-10 so you should be able to get that setup with you DSSI controllers if you have the necessary external cables.
 
I have many DSSI terminators, but I guess the trick is adapting the 50 pin cable to whatever the DSSI plug is so that a terminator can be fitted. I wonder what makes up a DSSI terminator.
 
marmotking said:
I have many DSSI terminators, but I guess the trick is adapting the 50 pin cable to whatever the DSSI plug is so that a terminator can be fitted. I wonder what makes up a DSSI terminator.
Click to expand...

I took a look at one of my M7769 KFQSA boards and it has 3 removable 10-pin dual terminator arrays in SIP packages. If I read the part number correctly it is 4610M-104-121/281 which is an obsolete Bourns part where each of the 8 data bus lines has a 120 ohm connection to one of the common end terminals and a 280 ohm connection to the opposite end terminal. I suppose I could remove one of the arrays and double check the resistance values with a meter, and also double check an array from another M7769 KFQSA board which appears to have DEC part numbers on the termination arrays.

Maybe the easiest thing to do would be to build your own terminator board which has a 50-pin header connector and a set of resistors on the appropriate bus lines. Might be difficult to find an exact replacement for the resistor array in small quantities so maybe you would have to use discrete resistors. Maybe it would be a good PCB layout project using surface mount resistors and have a few of them built up.

I took a quick look and didn't find an appropriate DSSI connector yet if you wanted to go the route of being able to use a DEC DSSI terminator. The connectors are the opposite gender of HD50 SCSI terminators. Then there is also the other DSSI connector style which is more like a double sided edge connector than a dual row pin connector.
 
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