Looking for help copying RT-11 V5 and XXDP+ to RX01 8" floppies

[bc17101]

Hi, I'm a new member to this forum.
I have a home built (Wire wrapped) PDP-11/05 that I built in 1974. I have fully restored it to full operation, but along the way I have zapped my diskettes due to a faulty write protect circuit in the floppy controller.
I would like to restore the floppies back to bootable form. To do this I need access to a local working system with an RX01 compatible floppy system or I could ship a box of 8 inch floppies (formatted)
to anyone that could help me copy the necessary files for RT-11 V5 and XXDP+ with some particular diagnostics that I would like to have. I will pay for all costs incurred.

Please contact me if you can help.
See picture of the system below.

Thanks in advance,

Bill

 

[Chuck(G)]

RX01 is simply bog-standard IBM 3740 standard (FM, single-sided, 128x26 spt). Anyone with an 8" drive attached to a PC and access to, say Imagedisk could run off as many copies as you'd like. RX02 is harder.

 

[MattisLind]

That was a very impressive build!

It would be very interesting to see more pictures and know more about this homebuilt machine. Is it a direct copy of the PDP-11/05? Is also the RX01 compatible drive a direct copy?

As Chuck write RX01 is possible to write using Imagedisk on an older PC with floppy controller and an adapter from 34 to 50 pin. Depending on floppy drive type you may need to enable the TG43 signal which only exists on 8 inch floppies. There is the Dbit FDADAP board that has a small microcontroller that can do this.

Then not all PC controllers are able to handle FM. Check in the lmagedisk registry or use TestFDC to verify that your controller can handle FM / Single Density.

 

[bc17101]

I took the DEC 11/05 schematics and built a wire wrap list exactly. The various bipolar roms including the microcode were typed into a home built PDP-8 ( also wire wrapped) and compiled and formatted for a paper tape to be loaded into a prom burner. I added the octal keyboard and display because I got tired of flipping switches. It’s sitting on a 28k core memory I adapted to work on the Unibus. It was hogged out of 1/4 inch aluminum, and has a walnut case( not shown). Recently I added a 28K sram memory because the core memory was getting to be somewhat unreliable. I also recently replaced 40 pounds of linear power supply’s and replaced them with 5 pounds of switching power supplies.
the floppy system is my own design. It has a custom microcoded processor, discrete formatter and analog phase locked loop. all made of 7400 series logic and bipolar proms. I designed it to be bit for bit compatible on the unibus and Qbus, I also wire wrapped an LS-11 using the original western digital chipset they made for DEC. All this was built in the mid to late 70 s. I’ll be happy to send more pictures tomorrow.

 

[daver2]

+1. That machine looks rather impressive!

Welcome to the forum.

I assume that you have repaired your disk interface now?

I am just wondering whether you could use something like PDP11GUI (or similar) to bootstrap your own physical disk with an image?

If not, I wonder whether we could write a utility that could be downloaded to a PDP so that you could send a bookable image down to a specified disk device, to be written block by block?

We have a utility like this for the Apple and Cromemco.

I will check the PDP11GUI documentation after I have woken up and had breakfast and see if it already does this...

Incidentally, where are you based?

Dave

 

[daver2]

Ok, I didn't get anywhere with that solution...

How many DL11-compatible serial ports have you got on your machine (in addition to the console)?

I am just thinking about booting via a TU58 emulator and then copying over to your floppy that way.

Dave

 

[vrs42]

The various bipolar roms including the microcode were typed into a home built PDP-8 ( also wire wrapped) and compiled and formatted for a paper tape to be loaded into a prom burner.

I'd love to see that PDP-8 build too .

 

[hush]

wow, that's some really impressive work, props and welcome to the forum! happy to have you

 

[Wildfire]

for your work !

So you do have an Unibus but no physical Unibus slot i assume ?
Well, maybe this would mean some extra work for you, but you would then be way comfortable working with the system:
You need to get Joerg Hoppe's UNIBONE:

UniBone

Joomla! - dynamische Portal-Engine und Content-Management-System

retrocmp.com

 

[bc17101]

I'd love to see that PDP-8 build too .

Here are the pictures for the PDP-8 I built-in 1973 (I was younger then!) Notice the paper tape 100 cps punch (Teletype Burpe).
The reel to reel paper tape reader was used to operate a random access Paper tape OS I wrote to allow you to pick from many programs on the reel.
The Selectric interface was a custom design to allow it to attach as a RS-232 terminal.

 

[bc17101]

As requested, below are some more photos of the PDP-11/05 as it was being built and later restored. The processor is the larger unit of sockets. The Unibus consisted of 2 connectors that have fixed I/O wires going to the back of the chassis. it is electrically a Unibus in every sense of the word but was Physically built from EECO wire wrap modules and holders. the Peripherals shown are a 4 channel RS-232 DL-11, Paper tape punch/reader, floppy disk interface (RX compatible but completely my own micro coded design shown in a separate picture with one of the first 8" Shugart 8" SA800 drives), interface for RK-11 compatible SMD disk (using Pertec 10MB fixed / removable disk), and a special interface for a board tester I used to use. The Core memory is a Standard Memories 32K by 18 bit unit with my custom controller for the Unibus which is attached to the side of the cage. I recently removed the linear power supplies and replaced them with switchers (40 pounds less weight!). I also added a 32K SRAM to replace the core memory for reliability reasons.

I love the DEC computers and was offered a job at DEC in California, but took the Emulex job instead for fear of having to move back to Mass. At Emulex I first worked as a designer and eventually became their Vice President of Engineering. I had the privilege of designing a MSCP Disk controller for Digital a few years before they went away.

I'll post another series of pictures later showing a wire wrapped LSI-11 with the Western Digital chip set they designed for DEC.
.

 

[BitWiz]

If you can provide me with the disk images (byte for byte files) I can write them for you on my greaseweazle.

I read and copy and copy RX01 and RX02 disks all the time on it.

 

[bc17101]

Thank you for your offer!!
I just received my greaseweazle today! However I still have to build the 34 pin to 50 pin adapter board and I have to learn how to use the program.
Do you get any of your files from bit savers? I see most of them are for RX02s which I can't read with my system. I was hoping someone could copy a few files from their RT-11 disks (most likely written on an RX02) and copy the basic necessary files to some RX01s I would supply. But that takes a system with an RX02. The only RX01 images I have found so far are for RT-11 V03 (which I would be happy to have now, but I was hoping to get the latest V5 version if possible. Right now my goal is to boot RT11 on one disk with Dungeo and its files so I can show my grand kids what a fun non graphics game is all about.

 

[BitWiz]

I might be able to create the necessary images under simh. I'm not an RT-11 user but it might be worth a try.

 

[BitWiz]

Thank you for your offer!!
I just received my greaseweazle today! However I still have to build the 34 pin to 50 pin adapter board and I have to learn how to use the program.
Do you get any of your files from bit savers? I see most of them are for RX02s which I can't read with my system. I was hoping someone could copy a few files from their RT-11 disks (most likely written on an RX02) and copy the basic necessary files to some RX01s I would supply. But that takes a system with an RX02. The only RX01 images I have found so far are for RT-11 V03 (which I would be happy to have now, but I was hoping to get the latest V5 version if possible. Right now my goal is to boot RT11 on one disk with Dungeo and its files so I can show my grand kids what a fun non graphics game is all about.

I am a PDP-8 guy and I got my images from the RX02 emulator and I created the rest myself from Serial Disk mounted RK05 Images and my RX02 on my PDP-8.

I have used the grease weazle to create bootable RX01 and RX02 diskettes from images. RX02 omages are 512,512 bytes and RX01 images are 256,256 bytes.

Since OS/8 uses a different disk and directory structure than RT-11, I would not be able to create the diskettes on my PDP-8.

I think SIMH can mount both RX02 and RX01 media. I've just never used RT-11.

 

[AK6DN]

The RX01 and RX02 for either PDP-8 or PDP-11 use the same basic low level disk format. Just sectors of sequential bytes:

o 77 tracks of 26 sectors of 256 bytes is 512,512 bytes total for RX02.

o 77 tracks of 26 sectors of 128 bytes is 256,256 bytes total for RX01.

PDP-11 / RT11 uses the bytes as is, so it uses all of the 128 or 256 bytes per sector.

PDP-8 / OS8 uses either 12b words or 8b bytes. Two 12b words are packed into three 8b bytes in normal 12b disk access mode.

So an OS8 sector uses just the first 3/4 or so of each sector, the remainder is either unused on reads or written as zeros on a write.

A PDP-8/OS8 in standard 12b mode is not going to be able to write a PDP-11/RT11 disk image since it can't access the last 1/4 of each sector.
You would have to use the drive in 8b mode (IDK if there is a way to tell OS8 to do this).
The hardware on a PDP-8 is certainly capable of doing this, so one could write a custom low level assembly program to do it.

The RX02_emulator for PDP-8/PDP-11 stores the full 512,512 or 256,256 byte physical image of a disk, whether 8b PDP-11 or 12b PDP-8 mode.
When running on a PDP-11 in 8b mode, it uses/returns the full contents of each sector as a sequence of 8b bytes.
When running on a PDP-8 in 12b mode, it packs/unpacks the OS8 64w or 128w sector into the 92 or 196 8b bytes, and zero extends to the 128B/256B sector size on the write to the disk.