6 Feb
2000
6 Feb
'00
11:05 a.m.
On Feb 6, 18:18, Allison J Parent wrote:
<In RT-11, full MSCP support post-dates even 5.1.
5.1 works with
RQDX1/2,
define full?
Supports all the QBus controllers. OK, that's not very full :-)
<but not RQDX3, for example; because whoever wrote
the DU: handler
ignored
Dont tell mine RT11 V5.01c system then as the RQDX3 runs just fine. To
the best of my knowlege RQDXn are interchangeable
Maybe it depends on the firmware then, but I can assure you that the bug
certainly exists, and lots of people other than me found it and suffered
from it. The particular bug is that the RQDXn (and
other MSCP controllers)
return some flags in the top 4 bits of the SA register
during
initialisation. On the RQDX1 and RQDX2, the rest of the register contains
zeros, and the driver code depends on that -- IIRC, there are three places
where it does a BNE on the result. The RQDX3 of the same vintage as 5.01,
however, returns the interrupt vector in the bottom bits of SA, so the BNE
doesn't work as desired. Actually, there's slightly more to it than that,
but that's the basics.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York