>>>>> One Without Reason writes:

Sridhar> Sort of.  It supports the S/390 G4 and higher.  Doesn't support the S/390
Sridhar> G1, the ES/9000, or others.  Basically what I am doing is to move all the
Sridhar> code for the S/390-Ri4+ instruction set onto its own compiler flag.  
Sridhar> Finding exactly where all these instructions are is taking time.  It'll
Sridhar> take me another month or so.  When I am done, though, I will be able to
Sridhar> get the NetBSD kernel working on any IBM mainframe newer than the ES/9000
Sridhar> 9021, and maybe even older systems than that.

	I assume that you are aware of the S/390 "Principles of Operation"
documentation available on IBM websites as HTML, PDF, and BookMgr format:

http://publibz.boulder.ibm.com/

	Documentation for all generations of the S/390 architecture are
online for comparison, including details of changes in the introduction of
each revision.

	I believe that one of the dependencies on G4 and above for Linux
kernel support was the addition of a privileged instruction for SMP
support.  For a UP kernel, NetBSD (and Linux) could run on an earlier
generation system.

	It would be wonderful to modularize the GCC support to allow
runtime choice of S/390 generation, and even S/370 support.  Merging the
GCC "i370" port into the s390 port would be great.  That work was not
within the mandate of the IBMers who developed the port.

David