How much do SCSI controllers typically know of SCSI (as opposed to the
knowledge being in host software)?

I suppose that depends on the hardware platform in question.  So here's
why I ask....

I was thinking about connecting two SCSI buses with the data wires
switched around, so that one bus's D7 (and therefore ID 7) isn't the
same as the other's.  This would allow me to take two machines with
internal disks and plug them together through their external SCSI
connectors.  (For the moment, I am prepared to depend on the human
layer to avoid problems from both hosts trying to access a drive at the
same time.)

This would of course demand hacks in the SCSI code to run all data
bytes through a mapping to re-order the bits, at a minimum - but it
won't work if the SCSI chip itself knows too much about SCSI, because
there'll be no way to teach it about this.

Thoughts?  Or is this too egregious a hack to be worth even thinking
about? :-)

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