[Simh] Disk sizing

[Mark Pizzolato]

On Sunday, February 5, 2017 at 2:48 PM, Timothe Litt wrote:
> On 05-Feb-17 16:15, Johnny Billquist wrote:
> > On 2017-02-05 21:31, Mark Pizzolato wrote:
> >> A concept related to this discussion is simh's auto sizing of disks.
> >> In the PDP11 and
> >> VAX simulators the RQ and RP disks use the sim_disk library to
> >> perform I/O to disk Images and/or physical disk devices.
> >
> >> So, I'd like to expand the set of file system types that the auto
> >> sizing logic can perform to include RSTS disks and whatever might be
> >> commonly used with RSX and RT11. I can certainly give all the
> >> information you need for ODS-1, which is what RSX use. The structures
> >> are pretty similar to ODS-2, so if you already have that, it should
> >> be very simple to add the ODS-1 stuff.
> > Unfortunately, this will only cover RSX systems. For RT-11 (as well as
> > RSTS/E and others), you'll have to get someone else to help. I suspect
> > Paul should know RSTS/E, if he just have the time.
> >
> > Anyway, the gist in ODS-1 is that the size of the device is contained
> > in a file called BITMAP.SYS (FID 2,2,0). In there, there is a 32-bit
> > value saying what the size of the disk is in logical blocks.
> >
> For ODS-2, you want the SCB, which is contained in BITMAP.SYS.  It gets tricky,
> especially where geometry is involved and where the emulated disk image is a
> physical copy of media that doesn't match the SCB.
> 
> I have code that navigates ODS-2 and attempts to identify the correct disk
> based on the recorded geometry.  It's part of an ODS-2 reader/writer.  I need
> to get back to that project and finish some higher-level stuff; when it's released
> you can extract that code for SimH.  It's about 5 down on my stack, which I'm
> unlikely to reach before April/May.

I've already done the ODS2 case and the Ultrix case, so nothing needed for that.

Now that Johnny pointed me to the ODS1 spec, I'm adding the appropriate file 
system structure definitions right now.   I have enough to solve this case.

- Mark