>> What boards are at IPL6?  I thought the A3000 and A2091 controllers were 
>> both IPL2.
>
>  The Progressive Peripherals Zeus SCSI, and the Magnum 40 SCSI both use
>IPL6.  The MultiFaceCard serial ports also use IPL6.

Also the GoldenGateII bridge connects all ISA interrupts to INT6. The
ISA kit did not make it to 1.1 (I suppose interrupts being at level 6
can be blamed for that) but it does work for me (finally).

I'm not sure but I think that I might get overrepetitive keys
sometimes (or might be just shaking hands :)

I do not use LEV6_DEFER as I don't understand how it works. For
example with GGII those level 6 interrupts should (shouldn't they?) be
acknowledged (and maybe blocked) in the device causing them in the
real INT6 handler. This means that one can't schedule a lower level
interrupt without knowledge about the device which caused the level 6
interrupt. Isn't this what LEV6_DEFER tries to do?