[Simh] VAX emulator slow to configure extra disks

[Johnny Billquist]

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.

I think the 16-bit unit number fact is incorrect. If I remember right, 
it is a 12-bit number, and then you have a 4-bit subunit number, which I 
don't know if anything ever used.

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.

> Some operating systems may limit the supported numbers.  For example, RSTS allows unit numbers 0 to 15 for MSCP disks.  And it supports multiple MSCP controllers, but the unit numbers must be unique -- unlike VMS which allows DUA0 and DUB0.

I haven't checked, but I sortof suspect that RSX won't like unit numbers 
above 255. But at least in RSX-11M-PLUS, unit numbers do not have to be 
unique. As I mentioned, there is an extra mapping layer between the 
device unit numbers in the OS, and the physical unit numbers on the 
disks. And there is no correlation between them.

In addition, RSX-11M-PLUS also have a naming scheme like VMS which is 
used by the reconfiguration tool, so you can also see names like DUA0: 
and DUB0: if you look in some places. But in normal operations, you 
refer to the disks as DUn:, where n goes from 0 to as many MSCP disks 
you have, and are a separate numbering from the disk unit numbers.

   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