[Simh] SCSI-Interface for simh-vax?

[Johnny Billquist]

On 2018-09-02 20:05, Paul Koning wrote:
> 
> 
>> On Sep 2, 2018, at 5:55 AM, Johnny Billquist <bqt at softjar.se> wrote:
>>
>> ...
>>>> I wasn’t able to figure out how to make it work in RSTS/E.
>>> To be bootable, a CD needs an appropriate boot block (LBN 0).  For VMS,
>>> it's written by 'writeboot' - not initialize.  I don't remember the
>>> details for RSTS - look at SAVRES->RESTORE and BACKUP for
>>> possibilities.    Or wait for Paul K to fill that in.
>>
>> Paul needs to chime in here. But in the back of my head, there is a warning bell about RSTS/E expecting/require the boot device to always be writeable, which could be a serious problem for a CD.
> 
> No, that's fine, provided the file system flags mark the file system as read-only.  In that case, RSTS will treat the disk as an installation disk, and when booted go automatically to the installation actions as opposed to prompting for a regular startup.  You can't start such a disk, that is true.  But you can boot it, invoke the disk initializer to initiaze your intended system disk, and copy the minimal files from the CD to that disk after which it is booted.

Ok. Definitely sounds like it should work then.

> The block size could be a consideration; RSTS expects 512 byte blocks and I don't know how one would work around that on a CD.  Also, what interface would you use?  MSCP, I suppose; does that do the necessary magic to make it look like a 512-byte sector size device?

This is the same issues/conditions as you face with RSX, which the OP 
did get to work.
Yes, you'd normally hook the CD to a SCSI controller which appears as an 
MSCP disk to the PDP-11 side. I've done that often enough myself as well.
You do need a CD which can deal with 512 byte blocks. But from there on, 
it looks just like any other disk to the PDP-11. A VAX have the same 
issues/requirements, as do SUN. Not all CD drives can deal with 512 byte 
sectors, so you have to look for that.

   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