Several comments on crashed drive in PDP-11/23

[Philipp Hachtmann]

Hi,

> People around here are perhaps a bit paranoid on cleaning. :-)
I have no clean room and no cleanroom.....

>>Computer says:
>>
>>> **THIS VOLUME DOES NOT CONTAIN A HARDWARE BOOTABLE SYSTEM ***
>>>
>>>000034
>>>@
>>
>>I would be glad if that is a message read from the disk partitions (like
>>the bootsector message on non-system disks in my pc).
> 
> Yes, that is something that is read from the disk.
Great!

> RSX (don't know if the other OSes do the same) write a special boot block
> on non-bootable disks. This boot block basically just prints the above
> message, and halts. All that fits fine into 512 bytes.
Aha. I also have an RSX-11M license..... But no media or a clue how to 
get it into my machine.

>>What is the "modern way" to get software into the PDP11?
> Phew. Tape normally. Small, modern PDP11s usually have TK50, and software
> is distributed on TK50.
TK50...???

>>Is there anything like a RIM or BIN loader?
> Yes, but that is very old technology. People don't have paper tape on
> PDP-11, and haven't for a very long time.
Hm.... But I'm a paper tape enthusiast..... I just think about giving 
the 11 away again - perhaps it's too modern for me.....


> If you're on a bare system, with only disk drives to play with, then your
> options are limited.
I have a RX02 double diskette drive and a lot of disks....

> The best might actually be to pretend you have a
> TU58, which speaks through a normal serial line, but is a block device,
> which most PDP11 can boot from.
May the original bootstrap code boot from a serial port directly??


> Yes. The TU58 is a cheap block device, for which the hardware on the
> PDP-11 side actually is just a serial interface. Most boot roms know how
> to boot from one, and an emulator for the actual TU58 exist.

The standard ROM in my 11/23+ does not boot from tu58?

>>Can I boot RT11 or RSX11 from floppy???
> Yes.
Ok. that's the point where I try to start. I will make a floppy. Need an 
image and then I'll try to put the image to onto a floppy.

> 
> Oh, and I would probably try to align the drive correctly if I fooled
> around with it. You never know when another pack shows up which you might
> want to read.

I can't realign the drive because I don't have the alignment tools, 
control panel for the drive and an alignment pack. But I did not change 
the head alignment when I removed the heads. Left them together without 
moving relatively to each other..


Does anyone have experience with that "vtserver" program?
It puts it's bootcode into the pdp (via odt) and then the CPU stops. 
Sometimes a single 'r' character shows up. And sometimes I see an error 
message (non-existent record 13)....
I start to think about a problem with my serial port.... Are there known 
issues with the console port? I have tried 300,2400,9600 and 19200. 
Always errors. But NEVER while vtserver puts its startup code. Always 
after vtserver has started the pdp.

And a simple question: How does the addressing in pdp11 work? R7 seems 
to be only 16 bit wide. And when I boot up the system, the MMU should be 
off and the memory mapping should be direct. How do I access the upper 
bits of my PC (i.e. "changing the segment")?


Regards,
Philipp :-)