RE: What is the largest drive that NetBSD/VAX will support?

[Mark Pizzolato <Mark%infocomm.com@localhost>]

On Friday, February 19, 2016 at 12:00 AM, John Klos wrote:
> > I'm currently setting up a new project. In this case its an
> > arrangement of SIMH/VAX running on Linux/I386. The host has a Zip100
> > drive installed. And as it happens I'm wondering, with this issue:
> > "What is the largest drive that NetBSD/VAX will support?". Conversely
> > it becomes "What is the smallest drive that NetBSD/VAX will support?".
> 
> The largest drive it'll support without any extra fuss, I think, would be
> 2 TB (2^32-1 blocks of 512 bytes each). The smallest, I think, would be one
> sector.

That is indeed the upper limit.  I can't imagine any amount of 'fuss' which 
could extend it beyond that.  The boundary is based on the fact that the 
MSCP protocol has a 32bit field containing the logical block number (thus 
the 2^32-1) and all sectors are 512 bytes.  This is a limit of the hardware being 
simulated due to the structure of the MSCP protocol.

> > That presupposes I can successfully point the program to a Linux
> > device driver who itself is connected to that physical drive.
> >
> > Obviously for the mechanics of such things I'll have to ask on the
> > SIMH list. That's next.
> 
> It should be possible to give SIMH a whole device such as the GNU/Linux
> equivalent of NetBSD's /dev/rsd0d. I've done this when using an SD card
> which was the boot disk of a real VAX with SIMH on NetBSD through a USB
> card reader.

Simh has 2 mechanisms which can access a device.  The default SIMH mode
uses stdio (fopen/fread/fwrite/fseeko/fclose) to access the simulated disk 
image file.  The RAW mechanism uses open/read/write/lseek/close to access
the simulated disk.  RAW mode disk sizing is done using lseek(f, (off_t)0, SEEK_END);
if that works on your device things should work well.

- Mark