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

On 2016-02-21 15:45, Mark Pizzolato wrote:
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

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

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.

That was not entirely clear. The question, as stated, is "What is the largest drive that NetBSD/VAX will support?", while the question was posed by someone running simh/vax.

But yes, at the moment, simh do not support scsi for VAX, so for simh, there is a limit of 2^32 blocks, based on MSCP limitations.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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