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

On Sunday, February 21, 2016 at 4:49 AM, Johnny Billquist wrote:
> On 2016-02-19 14:25, Mark Pizzolato wrote:
> > 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.
> Noone forces you to use MSCP. There are VAXen with SCSI as well.
> However, disk labels also limit you to 2^32 blocks, or something like that, so
> there are several subsystems that might cause issues with larger disks.

No one would force you to use MSCP, but since this question was 
specifically about simh and the only large capacity disk interface which 
any simh device simulates is the MSCP rq device, SCSI isn't a choice on 
any current simh VAX simulator.

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