SASI interface, SCSI devices...

From: Jules Richardson <>
Date: Wed Feb 9 14:20:17 2005

On Wed, 2005-02-09 at 14:22 -0500, Steve Jones wrote:
> Briefly Googling left me with the impression that hooking a
> SASI device to even an old SCSI contoller is pretty dicey, but
> no good feel for how well a random SCSI device might work with
> a SASI controller.

I can't remember whether ten-byte commands were there from the start or
if they're a SCSI / CCS thing - but if driving a SCSI disk against a
SASI controller *probably* doesn't matter.

I think the ability for a host to reserve a device only came in with
SCSI, but again it shouldn't matter in the case of SASI controller and
SCSI device.

There's a big amount of protocol overlap; it's just that SCSI supports a
few extra commands. I reckon you could get away with a SCSI device
driven by a SASI controller - and *probably* a SASI device driven by a
SCSI controller, providing you code your drivers not to use any SCSI
features. (Linux drivers, at least the Adaptec ones, expect a reply
back from an Inquiry command on a device before they'll think about
talking to it, which screws up talking to a lot of very early SCSI
devices - or SASI - which don't support Inquiry)

By the way, I believe a lot of home micro kit that had the ability to
talk to SCSI/SASI devices expected them to be low level formatted to 256
bytes / sector, which these days most (all?) drives complain at. If
you're trying to hook a SCSI disk up to something there, then you'd have
to hack the driving code to use 512 byte sectors with 50% wastage (not a
big deal given the size of modern disks) or cleverly pack data 2 logical
sectors to one physical (probably not worth the coding effort)


Received on Wed Feb 09 2005 - 14:20:17 GMT

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