[Simh] Subject: Re: something strange with simulated RK05 drive ?

[Henk Gooijen]

Thanks for responses, I learned a few things!
(I can only respond when I am at home, sorry for the delay)

The first (big) eye opener for me was that RK11 registers in SIMH are
of course *not* the same as the RK05, duh!  Good to know for future
projects!
I knew about the error conditions on the RK05 drive that turn on
the FAULT indicator, but in SIMH_PiDP-11/70_simulated-RK05 it is
difficult to break the positioner glass or have a burned-out lamp 😊
So maybe the FAULT indicator lights up for a few reason that could be
plausible, but are in fact not correct as they are RK11 errors and not
RK05 drive errors!  Maybe I can get away with saying that the simulated
"RK05 drive" is a drive plus controller …

What I also learned is that (at least in SIMH) you do not need to
FORMAT a new RK05 disk (container file)!  Just an .INIT RK0: will do!
However, initially I could not get the RK05 simulation working, so
I got stuck on FORMAT (the reason was a stupid mistake on my side).
When I enter the .FORMAT RK0:  command, I see the ONCYL, RD and WT
LEDs flash and flicker for quite some time. When I enter .INIT RK0:
ONCYL flashes once, and RD and WT flash briefly.
I tried in a "virgin" SIMH environment and Bob is (of course) correct.
You do not need to FORMAT an RK05 in SIMH!  But it does actually format.
However, it does so until it goes outside the range of valid cylinders.
I guess that can be fixed, but as Bob says: don't do that 😊
On my (long) "to do" list: "why format tries to write cylinder 203"?

I understand that the behavior of the lamps on my "simulated RK05"
completely depends on how I added code for that in pdp11_rk.c.  But it
seems OK to me, because when I boot RT-11 from that simulated RK05 drive
ONCYL and RD flash most of the time, but WT also flashes a few times.
Long ago I booted a (real) 11/34 using Don North's tu58em with diagnostic
printout and (to my surprise) during the boot a few writes occurred.

At the moment I cannot verify with a real RK05, because the temperature
in my "museum" is a bit low to run a real RK05 (just 10 degrees Celcius).
My current implementation turns on the FAULT lamp for several reasons.
- for the RK11 errors (so I need to check and somewhat improve that),
  although the errors are not likely to occur in SIMH, unless you are
  programming access to the registers directly and make a mistake ...
- if the drive (or software!) sets the drive to "read-only" (thus the
  WT-PROT lamp goes on), and you do some write action, for example, try
  to delete a file, the FAULT lamp goes on.
  Toggling the WT-PROT switch or (RT11 command) .SET RK0 LOCKED will
  turn on the WT-PROT lamp. Toggling again or .SET RK0 WRITEENABLE will
  turn off the WT-PROT lamp.
- according to RK11/RK05 documentation, toggling the WT-PROT or the
  LOAD/RUN switch (to RUN) will turn off the FAULT lamp.

I am having fun with this project and learn a lot as I go.
Also, thanks to you guys!
Henk

PS. Printing a 3D scaled RK05 cartridge is in progress. When that is done
I will try to make my first YouTube video …

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