KZQSA and disks, was Re: MicroVax II question

From: Fred N. van Kempen <waltje_at_pdp11.nl>
Date: Tue Jan 6 14:08:15 2004

On Tue, 6 Jan 2004, Lyle Bickley wrote:

> Here's another "interesting" point - a VMS HDD created by the Emulex UC07 or
> KZQSA is compatible with either the KZQSA or UC07.
>
> I could hardly believe it - but the same SCSI HDD created from either will
> boot and run VMS from either...
Well, a SCSI device does its own low-level formatting and bad
block management and interleaving, so, pretty much is a box full
of data blocks to the controller. So, the controllers only have
to address those blocks, and nothing else- this would indeed
allow to "share" the layout between controllers, as is quite
normal for SCSI devices these days.

Although the UC0x controllers use KDA50 emulation, they do this
towards the *host*, not the *device* end, so probably don't do
anything weird at the device end that would make them incompatible
with the other controllers, such as the KZQSA. Which, if memory
serves me right, was just an NCR 5340 or 5380 atop a Qbus bus
interface..

--f
Received on Tue Jan 06 2004 - 14:08:15 GMT