IBM to support UNIX on 4300

[Herb Chong [DCS]]

In article <759 at amdcad.UUCP> phil at amdcad.UUCP (Phil Ngai) writes:
>> With all this talk about IBM's port of UNIX to the 370's, what about the
>> version done at ATT?  It is described in pretty good detail in the Oct 84
>> BLTJ.  Essentially, they got IBM to make some mods to TSS, and then put
>> Unix on top of it. TSS deals with the i/o hardware and paging, Unix does
>> everything else.  This isolates Unix from different hardware configurations
>> (I/O channels, etc).
>
>You must be kidding if you are proposing to run anything except
>VM/CP on a 370 type machine. How many machines run TSS? Very few
>I bet.

i know of a few machines running TSS/360.  aside from running on a
faster on a s/370 machine, you gain almost nothing.  you lose
capabilities of having more than 6 channels, hardware support of
virtual addressing, and other performance enhancements that work in
microcode.  in short, you run TSS/360 because you have to and not
because you want to.  IBM no longer supports it so you live with all
the bugs unless you want to fix them yourselves.

there are compelling reasons for running IX/370 in a VM environment.
there are only a few possible types of interrupts that a virtual
machine receives: i/o, timer, svc (traps), diagnose (for VM services)
and external (console commands).  receiving any other types of
interrupts is a fatal error that indicates something drastically wrong
in the CP component of VM that manages the real machine.  thus, all
code to do with error recovery in the unix kernel that are hardware
related can be completely thrown out as they will never be needed.
IX/370 doesn't have any and probably never will.  why duplicate
function when that sort of code is completely redundant.

also, the spool manipulation commands of CP are heavily used to handle
real i/o to printers and other such devices.  again, more code is
redundant and not included in IX/370.  the CP environment insulates the
IX/370 machine from both hardware problems and changes in hardware.

the device driver interface assumes that it is working with real disks
that are physically blocked at 4K no matter what device it's on and the
real devices can be shared with other virtual machines running other
systems.  there are facilties builtin to communicate with other virtual
machines whether they are running IX/370 or not.

IX/370 will run on VM in a 370-XA environment which has a drastically
changed I/O architecture from S/370.  the VM interfaces ensures
transparent I/O functions while providing many of the benefits of the
new structure.

Herb Chong...

I'm user-friendly -- I don't byte, I nybble....

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