[Simh] EXT :Re: VAX emulator slow to configure extra disks

[Hittner, David T [US] (MS)]

IIRC, the large HSx controllers could define a controller offset number that was added to the individual drive numbers. This would allow multiple HSx controllers to have large non-overlapping disk ID numbering using 8-bit drive plugs: ie. HSx1 at offset 0 could have drives 0..255, HSx2 at offset 256 could have drives 256..511, etc. Not many sites had that many hard drives, although I remember seeing one client that had a massive disk farm attached via HSx controllers..

I seem to remember that the KDA50 or RLV12 controllers had a set of internal dip switches that allowed the same sort of offset disk numbering functionality, but I am not sure. 

David

-----Original Message-----
From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Johnny Billquist
Sent: Monday, June 24, 2019 1:36 PM
To: simh at trailing-edge.com
Subject: EXT :Re: [Simh] VAX emulator slow to configure extra disks

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
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