[Simh] Largest VAX / PDP disk sizes

[Tim Shoppa]

Jason Stevens <neozeed at gmail.com> wrote:
> Hmm what is weird is that when I look at the disktab from any BSD and
> compare it to the table in pdp11_rq.c they don't agree....

Doesn't matter for MSCP disks. They're "just a bunch of blocks" and
accessed by block number.

Unless the device driver has to do host-side bad block replacement, which
you do not want to get into, and do not have to get into in the
emulator world!

> While looking up the RP06 I find this:
>
> pdp11_rp.c
>
> #define RP06_DTYPE      3
> #define RP06_SECT       22
> #define RP06_SURF       19
> #define RP06_CYL        815
> #define RP06_DEV        020022
> #define RP06_SIZE       (RP06_SECT * RP06_SURF * RP06_CYL * RP_NUMWD)
>
> and in the disktab:
>
> rp06|RP06|DEC RP06:\
> 	:ty=removable:ns#22:nt#19:nc#815:\
>
> Which do agree....

For SMD/Massbus drives, the physical geometry does matter to the driver.
I/O requests are issued based on physical track/cylinder/sector.

Tim.