> On Fri, 5 Mar 2004, John Hudak wrote:
>
> > Ahh yes, RK07 did have hardware support for dual porting...but...I don't
> > think any of the DEC OSs took advantage of it..That was why I decided to
> > write one in my spare time to run under RT-11.....waaaaaay long time ago....

>
> RSX does. As does VMS. But it only uses it for two controllers on the same
> machine. Dual-path disks. If you want to access a disk, and the controller
> is busy, the OS will go to the other controller and try.
>


RSX does and one of my old customers when I was at DEC used it dual
ported between machines. I think they used 11M -- but they also
had IAS...

> So: no loosely coupled MP machines that way...


I think they were interested in failover not MP.
If you're testing jet engines you may only have one chance to get
certain data. They definitely had two cpu's hooked to the disk
through different RK611s. DEC had them under contract and they
drove DEC nuts over it.

The dual port diags failed on the
11/70s due to timing problems (the diags had timing loops
that probably never were tested on the 11/70) and failed but the OS
ran error free. The engineers there were unhappy that the diags failed
even though the software worked perfectly. Diag engineering
pretty much didn't care (it was the mid 80's) and the 11/70 and RK07's
were out of production.

>
> Hmm, I wonder if not MP RSX could have the controllers on different CPUs
> though... But I'm not sure if the I/O scheduler were smart enough to
> always first try to use the local controller when there were to paths to
> the disk.
>
> Johnny
>
> Johnny Billquist || "I'm on a bus
> || on a psychedelic trip
> email: bqt@update.uu.se || Reading murder books
> pdp is alive! || tryin' to stay hip" - B. Idol

--
d|i|g|i|t|a|l had it THEN. Don't you wish you could still buy it now!
bpechter@shell.monmouth.com|pechter@ureach.com
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