[TUHS] UNIX on S/370

Larry McVoy lm at mcvoy.com
Tue Nov 21 09:45:15 AEST 2017

On Mon, Nov 20, 2017 at 06:43:28PM -0500, Ron Natalie wrote:
> > I get that PDP-11 and VAX used memory mapped I/O but was that somehow
> exposed above the device driver layer?  If so, I missed that, because I had
> no conceptual or technical problem with talking to an I/O 
> > channel, it was pretty easy.  And I suck at writing drivers.
> There's nothing that restricts a device driver to memory mapped I/O.    You
> do what ever you have to do to initiate the I/O.   Even the x86's originally
> used special instructions to start the I/O (in/out).    The DENELCOR HEP
> supercomputer (we did this port around 1983) we had to bounce I/O requests
> off a separate I/O processor different from where the kernel was running.
> Similar constucts were used on other machines.

Yeah, that's what I thought.  But other people were saying that I/O
processors and Unix didn't mix.  I don't get that, seems like whatever
the model is is hidden under the driver, that's the whole point of the
driver design is it not?

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