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PDP-11/23 adventure begins

Matt,

I would think that the least important device, from an interrupt priority standpoint would be the console. Among the most important would be disk controllers.

I usually put the memory closest to the processor, followed by disk controllers, followed by other stuff (A/D, D/A, HPIB) interfaces. I put the SLU interfaces at the end. Of course, in your backplane, the very last slot has to be the BDV11.

Yes, you have an H9273A. I too have the same BA11-N chassis.

Lou
 
Your find got me inspired to work on my own PDP-11/23 which has been standing for a while untested and with missing cards. I too have the BA11N, KDF11 and MSV11. So, given the cards and how they are placed in the backplane, I think I can safely say that you have a H9273 backplane (There should be a sticker on top of the backplane), which is straight. So if you just keep the cards in the order they were in to begin with you should be fine. If you have problems starting it, you can remove cards to isolate the problem.

I have spare DLV11 cards and probably a cable too. I didn't say anything before since I've been unable to test them. But yesterday I got my 11 working, and now I can :)

So if your other source of DLV11 doesn't work out, maybe we can work something out. I'm generally not that interested in money and would rather make a trade for something interesting. Send me a PM

(notice that I'm in Sweden).
 
Up and running...

Up and running...

Okay - my DLV11-J was shipped by ox cart but eventually arrived. It had been configured
so that Ch3 was not the console, and had Ch0 at 9600 baud and Ch1..3 at 1200 baud.
But with my trusty wire wrap tool I restored it to the factory defaults, threw together a cable and got into ODT:
@1000/000000 112701
@1002/000000 52
@1004/000000 105737
@1006/000000 177564
@1010/000000 1774
@1012/000000 110137
@1014/000000 177566
@1016/000000
@1000G*
001020
@
Yep... it works!
 
matu said:
Okay - my DLV11-J was shipped by ox cart but eventually arrived. It had been configured
so that Ch3 was not the console, and had Ch0 at 9600 baud and Ch1..3 at 1200 baud.
But with my trusty wire wrap tool I restored it to the factory defaults, threw together a cable and got into ODT:
@1000/000000 112701
@1002/000000 52
@1004/000000 105737
@1006/000000 177564
@1010/000000 1774
@1012/000000 110137
@1014/000000 177566
@1016/000000
@1000G*
001020
@
Yep... it works!
Click to expand...

Nice, hmm I should learn to use ODT properly, doesn't look that hard.
 
RX02 help?

RX02 help?

I'm having trouble with the RX02 drives - I can initialize the controller but when try to issue a read or format command, I get back definitive error code 120: "A PREAMBLE COULD NOT BE FOUND". The RX01/RX02 pocket service guide suggests that this could be due to the diskette, R/W electronics the drive, the controller, the power supply or the interface module, which doesn't really narrow it down much. I did verify that both drives are spinning and the head engages when I issue commands. The left drive makes a rattling noise when I close the door but the right drive sounds fine. I think the controller is fine because I can fill and empty the buffer without any problems and all the status bits come back as expected. The +5, -5, +9.5 and +24 volt supplies are all okay.

Does anyone know what the most common problems with these drives might be? Presumably there are some optical components that should be easy to check... or is it true that RX02 drives need pre-formatted media from DEC? My spare 8" floppies are from IBM...
 
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The RX02 can format floppies. It was for the RX50 that DEC wanted you to buy their floppies (and so they told you an RX50 drive could not format floppies. However, this is not quite true, because a Rainbow can format RX50s.)

Under RT-11, use the FORMAT command.

Are you trying to read a known formatted floppy, or are you starting with a blank?

Have you cleaned the heads? They may be filthy. Also, make sure that the head load arm foam is still intact. You should also run the XXDP diagnostics on these drives to see what they have to say.

Lou
 
Well, I haven't actually booted RT11 - I was planning on entering a program in ODT to write an RT11 boot image to a floppy, but haven't got that far. Here's what I've got:
Code: 
@1000g
RXV21 format.
0.  Initial state.
    RX2CS = 004000
    RX2ES = 000000
1.  Initialize RXV21.
    RX2CS = 004040
    RX2ES = 000004
3.  Issue read error code.
    RX2CS = 004040
    RX2ES = 000000
    BUFFER[] = 000000 000000 000400 006400
4.  Issue format command.
    RX2CS = 104440
    RX2ES = 110000
5.  Issue read error code.
    RX2CS = 004040
    RX2ES = 000000
    BUFFER[] = 000120 000000 000400 177440
002372
@
The '120' is the authoratative error code for A PREAMBLE COULD NOT BE FOUND.
The disks I have were formatted 30 years ago, but I expected to be able to read something at least even without formatting them.
 
If you think there could be something good on those floppies, don't reformat them. 30 years is no problem, they should still be readable.

You might have an easier time using Will's TU58.exe and a bootable RT-11 TU58 image. Once you have RT-11 booted off the emulated TU58, you can try to look at the floppies (and read them if they are RT-11 format), and then also make your own, new bootable RX02 system disks. The boot roms on your BDV-11 have the TU58 (device DD: ) bootstrap.

Did you have or find any bootable RL02 packs?

Lou
 
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Yes, I'd avoid wiping the floppies just yet if you can help it. The TU58 emulator is a great tool to get a minimal system running and can even be used to run XXDP diagnostics (I've done this on my '23+).

For reading and writing disk images, you may want to look into VTServer which can be used to pump data over a serial line.
 
Well, here's another possibility... the RX02 is a single-sided drive and the disks I have are double-sided. That means that the index hole is in a slightly different location and indeed, I don't see any index pulses from the MC1414 comparator that is driven by the photosensor for the index hole. The photosensor works because I see the output when I insert or remove a disk.
 
I cut a new index hole in the right place for a single-sided disk. Now I get pulses from the index comparator and after I set the RX INIT bit in the CSR I now see that the DRV RDY bit is set in the status register (it wasn't before). So that's progress... I can format track 0 in single or double density, and read it back again in the appropriate density, but the format function still never gets past track 0...
 
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I blame the media

I blame the media

I've learned more about RX02 drives than I ever knew I wanted to know and found out that there is a lot I took for granted many years ago. Indeed RX02 drives do not format their media. Although they could, the firmware in the M7744 controller board doesn't. Track 0 is special, but the other tracks need to have preformatted RX02 preamble data on the tracks in order to do anything useful, and the 'Set Media Density' command needs to find the preamble before it will write the density information to the header and zero the data on the sectors. These issues seem to be covered fairly well in http://www.classiccmp.org.

Anyway, I'm able to read any track I want on some bona fide RX01 formatted disks I borrowed. Making more RX02 disks from unformatted single sided media seems to be an adventure in itself, but at least it is well documented.
 
The DSD440, which was a non-dec RX02 clone can format RX02s without being attached to a computer. It has a sophisticated controller with various on board diagnostics and includes a formatting function. I have two of these (one working, one waiting for me to get around to repairing it.)

If you are really in a bind, I can mail you a bootable RT-11 RX02.

I would like to hear more about your technique for making a new sector hole at the single sided location. I have quite a few brand new DS disks that I want to use as RX02s. I know where the SS sector hole is supposed to go, but I would want to make the new holes in some kind of clean way and without scratching the media. If I make two sets of new holes, I can make these into flippies.

I have (when desparate) opened the jacket of a hard sectored floppy, taken it out of the jacket, and covered all but one of the sector holes to make a soft sectored floppy. That was a royal pain. I have thought about taking the media out of these DS disks, then punching a new sector holes, then putting the media back.

Lou
 
Making the SS sector hole was an act of desparation, but here's what I did... I had a head cleaning disk that had both index holes, so I used that as a template, marking the new hole location with a Jiffy Marker. Then I stuck two pieces of kapton tape together and slid it from the hub hole under where the index hole would go so as not to damage the surface of the disk when I cut the holes on each side with a razor blade. I think this is actually quite safe - there is no data recorded on that part of the disk so as long as there is no mechanical damage and the disk still turns and doesn't have a nick that snags on the linder then everything should be fine. This could get tedious if you have a whole stack of disks but with practice I'm sure you could do 20-30 in an hour.

Here's my plan for making my own boot disk... I compiled SimH from http://simh.trailing-edge.com and can boot RT11 using one of the archived disk images. After making my way though the RT11 system generation manual I'll create a simulated RX02 boot image, and then copy the sectors of this to a real RX02 disk and try to boot with that.
 
Now running RT-11

Now running RT-11

The details are long, but here's basically what I did...
1. Write an assembler for the KDF-11AA... this was just a quick hack to produce data that can be written to memory using ODT. With C++ strings and standard template libraries this isn't that difficult (I call it "Hacro").
2. Write a program to format a floppy disk and download hex data sent over the console to a buffer, then write the buffer to the appropriate sector... http://www.physics.purdue.edu/~mjones/pdp-11/rx02_write.lst
3. Install the pdp11 simulator from SimH on a machine running Linux. Create an RX02 boot image from one of the RL images. This contained a rather limited set of files as it was only a proof of principle. You can verify that this image boots on an RX02 drive using the emulator.
4. Dump the disk image to the real floppy in the RX02 drive. This takes a while at 9600 baud.
5. Here we go:
Code: 
@173000g
 28
START? DY0

RT-11SJ  V05.00
?KMON-F-File not found DK:STARTS.COM

.DIR

RT11SJ.SYS    73P 12-Mar-83      SWAP  .SYS    26P 12-Mar-83
TT    .SYS     2P 12-Mar-83      DY    .SYS     4P 12-Mar-83
TECO  .SAV    50P 12-Mar-83      DIR   .SAV    19P 12-Mar-83
MACRO .SAV    60P 12-Mar-83      LINK  .SAV    49P 12-Mar-83
TT    .MAC     7P 12-Mar-83      DY    .MAC    22P 12-Mar-83

 10 Files, 312 Blocks
 662 Free blocks

.R TECO
*IBASICALLY WORKS...$$
*B$$
*V$$
BASICALLY WORKS...*

So it more or less works... next I need to build a useful boot disk and see if I can figure out what's up with the RL02 drives.
 
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