[TUHS] running BSD 2.11 on my PDP 11/70 emulator

[Folkert van Heusden]

1. sounds like a calculation bug of some sort. possible, but not likely: 
I patched simh to output a set of large JSON-files with tests and their 
outcomes so that I can verify my emulator with the gold standard of pdp 
emulation without simply copying the simh-code (hopefully one day I can 
produce that set with a real hardware pdp 11/7). sofar I fixed all 
problems I found (a few flag problems and handling of the PSW).

2. yeah I have a suspicion that it might be a problem in one of the more 
complex addressing modes (@xxx(R7) for example where some of it comes 
from I space and some of D-space). am writing tests or that now.
regarding the 11/45 versus 11/70: I set the cpu to 11/70 when verifying 
the disk-image with simh. so it should run in a 11/70.

3. if I do that, the "avail mem" goes down with it, user mem stays 
307200.

[1*: 
https://vanheusden.com/git/folkert/simh-testsetgenerator/src/branch/valgen 
look for test.c]

On 2025-04-07 14:02, Kenneth Goodwin wrote:

> To me it looks like a memory issue of some sort. Setup of the MMU etc.
> 
> 1. Your user memory is less than 10% of "available memory" which should 
> be the amount left after the kernel loads and allocates dynamic  
> buffers. User memory should be alot closer to available number. Unless 
> it is referring to limits of mmu per process and not total available 
> for all user level programs.
> 
> 2. The bulk of the text dump seems to just be random initialized data 
> dumped from Ram.
> Aka - Printf() format strings.  Indicates that the wrong address in 
> memory is potentially being accessed.
> 
> Perhaps the pdp11 emulator configuration does not have a correct mmu 
> for your image file.
> 
> For example,  you are running the 11/70 emulation and the binary image 
> you are running is actually compiled for a pdp 11/45.
> 
> The 11/70 has an mmu supporting split instruction and data spaces. 64k 
> instruction,  64k data. But the kernel you are using was compiled to 
> run on a non split I And D version of the pdp11 supporting only 64kb of 
> combined user and data.
> 

[ this suggestion came from Kenneth's 2nd reply, added in this message 
to prevent a lot of reply-mails by me ]

> 3. If your bsd image has kernel dynamic buffer configuration limit 
> parameters,  you could tweak those down say 50% to see what happens.  
> (Not a BSD kernel hacker and it's been a while since I last read over 
> the source code)