[Simh] RE : RE : How to setup a simh VAX VMS cluster that handles more than 16 disks.

[Boucher, François]

Mr Pizzolato, I believe your are quite knowledgeable about simh!
you are sending me an interesting track to follow about the disk IO
optimisation.
 
It makes sense to me that buffered disk IO would create the described 
inconsistencies.  If one would like to bypass this problem, how would you
recommend to modify the source code?
Is there a replacement function that makes direct unbuffered IO to the
virtual disk container files that can be used in place of fwrite ?
I did not check very much this aspect of the code, but I find your inputs
very very informative.
 
I was also rethinking about the polling of the ethernet interfaces.
In the harware world, we would use an  hardware interrupt to trigger the treatment
of the receiving buffer.  In the simulator world, would it be possible to 
modify the source code of the simulator to do a software interrupt that
triggers the reading of the receiving buffer?
 
Thanks for your answers
 
Francois Boucher ing.
 
 
This "could" work as is if the I/O done by simh to the virtual disk
container files was NOT done with the C runtime library (fopen,
fread, fwrite, fclose), and was done with direct unbuffered I/O to
the respective file storage.  Currently the buffering done by each
simh instance leads to inconsistencies since each simh instance has
its own buffered data which the other simh instances have no
mechanism to synchronize.

- Mark Pizzolato


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