Advice on VAX peripherals wanted, note re HSC50

[Steve Glaser]

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I'd understood that the CI-780 and CI-750 interfaces to the VAXcluster
assumed that system software uses the page tables like VMS does (the
HSC50 is just part of the system, it hangs on the CI bus and talks to
disks and tapes).  The VAX architecture manual used to describe a
number of "reserved for software" bits in the page table entries and
Unix uses these bits differently than VMS does.  Apparently, the CI
series interfaces "know" about page tables, but assume those bits are
used the VMS way.  This would require changes to the 4.1 (or 4.2)
paging system to be usable.  I also think the DR-780 has the same
problem.

The new VM architecture of 4.3BSD may fix this (if it ever makes it).
DEC's product version of Vax/Unix may also fix this.  My understanding
is based on a conversation with Bill Shannon at the Boston USENIX - DEC
may have changed the hardware since then (It wasn't announced then
anyway) [Armando, are you listening?].

In any case, it's going to take more work than just writing another
driver, if only because it's another SBI (CMI) device so it doesn't fit
into the model of an ordinary Unibus or Massbus device.


	Steve Glaser
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