[rescue] zuluscsi wide sca80 or scsiknife sca as replacement to hd in sun ultra 60

[Nathan Raymond]

On Wed, May 27, 2026 at 3:14 PM vom513 via rescue <rescue at sunhelp.org>
wrote:

> > On May 27, 2026, at 2:30 PM, Dave McGuire via rescue <rescue at sunhelp.org>
> wrote:
> >
> >  Your logic is sound and ordinarily I'd agree with your point.  But many
> early Suns were shipped with ESDI drives and Emulex MD21 SCSI->ESDI
> adapters, and MFM drives with Adaptec ACB4000 SCSI->MFM adapters. Nobody
> called them "emulators”.
>
> Would this be considered an “interposer” ?  I watch a fair amount of
> vintage computer youtubers and hear this term.  I feel like Adrian’s
> Digital Basement mentioned it regarding his m68k based UNIX machine
> (Plexus).
>

Interposers are typically devices with minimal logic to support connecting
one device to another where form factors or connector types are physically
incompatible, and often where the device being adapted by the interposer
has a functional subset of the standard. For instance a SAS to SATA
interposer allows the use of SATA devices on a SAS controller. SATA devices
have a subset of the SAS standard. There are no interposers for using SAS
devices on a SATA controller because the SAS device has a superset of the
SATA controller's features. I'm not super-familiar with ESDI, but looking
it up in Wikipedia, they mention, "many high-end SCSI drives of the era
were actually high-end ESDI drives with SCSI bridges integrated on the
drive."

Bridge is the correct term for that I think, and interestingly that links
to the Wikipedia entry for "Protocol converter":

https://en.wikipedia.org/wiki/Protocol_converter

While modern SCSI emulators might be thought of as bridges/protocol
converters, that is only one part of what they do. Modern SCSI emulators
are highly configurable and support a wide range of physical device
emulation, can present many emulated SCSI devices which are all stored on
one modern device such as an SD card, and have specific user-configurable
controls over how the emulated SCSI devices are being presented to the host
and often include other ways to interface with the SCSI emulator outside of
the host, all of which define it as something much greater than a mere
protocol converter.

- Nate
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