[Simh] Getting rsxs to run on the pdp11 emulator

[Johnny Billquist]

On 2015-03-03 22:26, Rhialto wrote:
> On Tue 03 Mar 2015 at 13:05:50 -0500, Christian Gauger-Cosgrove wrote:
>> My simulator config is big, and somewhat redundant, I actually have
>> the installation phase and its tape swap automated with:
>> SET TU0 LOCK
>> ATTACH TU0 TAP\BB-J0830-01.M01_RSX11M+_V4.6_1999.tap
>> BOOT TU0
>> ATTACH TU0 TAP\BB-J0830-01.L01_RSX11M+_V4.6_BRU_1999.tap
>> CONTINUE
>> I have the tapes in a subfolder called "TAP". And I swap the tapes
>> between drives after the standalone boot tape has booted by just
>> hitting Ctrl+E just once.
>
> Nice trick! I've used it immediately in my test setup. This time I
> started with a configuration which is closer to the system I had set up
> already anyway.

Swapping tapes would/should be obvious, if people think about it. If 
that is what you did on a real system, you obviously need to do the same 
in the emulated one...

> After quadruple checking the csr and vector addresses (and no, if SHOW
> TU doesn't list them, it doesn't mean they are fixed and therefore
> correct; instead I had to do SHOW RHB to find the values. This might be
> a small point of improvement for simh; I could also use some help from
> simh to find out that connection, which may be obvious to the
> experienced, but it wasn't for me. I only discovered it by crosschecking
> device names in my running RSX system)

Something very obvious if you know the actual hardware.
I sense a problem here based on you trying to run and operate a system 
which you know nothing about. You will hit more problems that way. Might 
be worth researching a bit about actual PDP-11 systems...

A TU tape drive is a MASSBUS tape drive. As such, it do not directly 
connect to your system. The MASSBUS is a separate I/O bus. You then have 
a MASSBUS controller on your Unibus.

To make it even more interesting, the tape drive is not actually sitting 
on the MASSBUS either, but in reality there is something called a 
formatter, which sits on the MASSBUS. For a TU77, this would normally be 
a TM03. The TM03 can then, in turn, have as many as eight TU77 drives 
connected.

But form the CPU, the CSR and vector related are those of the MASSBUS 
controller.

> One difference that at first I did not understand, was that I got this:
>
> BRU - Starting Tape 1 on MM0:
>
> BRU - This disk will not contain a hardware bootable system
>
> BRU - End of Tape 1 on MM0:
>
> BRU - Starting verify pass Tape 1 on MM0:
>
> BRU - End of Tape 1 on MM0:
>
> BRU - Completed

Not sure why you would get that message, unless you were restoring a 
backup saveset that actually is not a bootable saveset.

> However, after reading the actual documentation :)
> AA-H431H-TC_RSX-11M-PLUS_4.3_System_Generation_and_Installation_Guide_Jan90.pdf
> I see that I need to swap the tapes between booting and running BRU.
> I didn't see that happening in your log file somehow, although you do
> mention it.

That is a different thing.
This is because back at V4.3, the BRUSYS standalone system was 
distributed on one tape, and the RSX system itself was on another tape.
So you mounted the BRUSYS tape, and booted from it.
Once it had booted, you removed this tape, and instead put the RSX 
distribution tape in the drive, and proceeded to restore from that tape.

The message about a hardware bootable system is unrelated to this.

Forthermore, by M+ V4.6, the two tapes were actually combined to just 
one tape, so you normally do not have two tapes, or switch between tapes 
during the installation.

	Johnny