[Simh] VAX emulator slow to configure extra disks

[Johnny Billquist]

On 2019-06-24 20:09, Mark Pizzolato wrote:
> On Monday, June 24, 2019 at 10:36 AM, Johnny Billquist wrote:
>> On 2019-06-24 15:12, Paul Koning wrote:
>>>
>>>
>>>> On Jun 23, 2019, at 4:44 PM, Mark Pizzolato <Mark at infocomm.com>
>> wrote:
>>>>
>>>> ...
>>>> As Tim mentioned, some of the hardware that is modeled did indeed
>>>> allow arbitrary unit numbers (via plugs on the drive).
>>>>
>>>> Some 14 months ago support was added to provide per drive Unit plug
>>>> values to be set.   This is set via:
>>>>
>>>>      sim> SET RQn UNIT=plug
>>>>
>>>> plug can be any value from 0 thru 65534.  Default unit plug for each
>>>> RQn is n.
>>>
>>> I know of 8 bit unit number plugs, in the RA series drives.  I haven't run into
>>> 16 bit unit numbers.
> 
> The field in the MSCP packets provides for 16 bits.

Yep. I wonder when I will ever learn to read the manuals instead of 
trying to trust my memory. It's 16 bits.
And I can't find anything about subunit numbers, so I wonder where I 
remember that from?

>> RA60, RA80, RA81 and RA82 had these large unit plugs, with 8 pins on them
>> that you could cut, so the largest possible unit number on those were 255.
>> However, RA90 and RA92 have a digital display, which you program the unit
>> number on, and they go to 4095.
>>
>> RA70 have 8 dip-switches to select unit number.
>> RA71, RA72 and RA73 must have a front panel, which sits on a SA7x box.
>> That front panel is also digital, and you have four displays - one for each drive
>> in the box. But even though they also could hold 4 digits, the unit numbers for
>> these drives wrap at 255.
> 
> There may be physical limitations on some hardware for different unit numbers
> with different drives, but the MSCP protocol and related software clearly support
> a 16 bit value.

Right. Like I said, some drives have an arbitrary or physical limitation 
to only 8 bits. But MSCP obviously supported larger numbers. And I was 
wrong saying 12 bits. It's clearly 16 bit if you read the documentation.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol