[Simh] VAX emulator slow to configure extra disks

[Mark Pizzolato]

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.

The logic in the KA655 boot ROM and VMS both probe for units increasing 
numbers all the way up:

        MicroVAX 3900 simulator V4.0-0 Current        git commit id: 0b67c268
        sim> set rq2 unit=49999
        sim> SH RQ
        RQ      address=20001468-2000146B, no vector, BR4, RQDX3, 4 units
          RQ0   159MB, not attached, write enabled
                RD54, UNIT=0, autosize
                AUTO format
          RQ1   159MB, not attached, write enabled
                RD54, UNIT=1, autosize
                AUTO format
          RQ2   159MB, not attached, write enabled
                RD54, UNIT=49999, autosize
                AUTO format
          RQ3   409KB, not attached, write enabled
                RX50, UNIT=3, autosize
                AUTO format
        sim> B
        Loading boot code from internal ka655x.bin


        KA655-B V5.3, VMB 2.7
        Performing normal system tests.
        40..39..38..37..36..35..34..33..32..31..30..29..28..27..26..25..
        24..23..22..21..20..19..18..17..16..15..14..13..12..11..10..09..
        08..07..06..05..04..03..
        Tests completed.
        >>>SHOW DEV
        UQSSP Disk Controller 0 (772150)
        -DUA0 (RD54)
        -DUA1 (RD54)
        -DUA3 (RX50)
        -DUA49999 (RD54)

        UQSSP Tape Controller 0 (774500)
        -MUA0 (TK50)
        -MUA1 (TK50)
        -MUA2 (TK50)
        -MUA3 (TK50)

        RLV12 Controller 0 (774400)
        -DLA0 (RL01)
        -DLA1 (RL01)
        -DLA2 (RL01)
        -DLA3 (RL01)

        Ethernet Adapter 0 (774440)
        -XQA0 (08-00-2B-DC-32-4E)
        >>>

> 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.

See above.

> 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.

> > 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.

The default unit numbers when compiled in the PDP11 simulator is:
   Device RQ goes from 0-3
   Device RQB goes from 4-7
   Device RQC goes from 8-11
   Device RQD goes from 12-15

When compiled in a VAX simulator the default unit numbers are 0-3 
for each of the RQ, RQB, RQC and RQD devices.

- Mark