On Tue, 24 Mar 1998, Tim Shoppa wrote:

> Isn't it harder than just writing the RLV11 device driver?  After
> all, you have to make sure that *nothing* else in the OS attempts
> to address any of the 15 "extra" copies of the RLV11 device registers
> that regularly occur every 256kbytes.  Doesn't this require a
> careful survey of everything else in the OS, and very likely rewriting
> some hairy things like I/O map allocations?  It'll probably also
> involve many unexplained crashes when other parts of the OS hit
> the extra copies of the RLV11 device register and prod it into doing
> something it shouldn't, and many many hours of debugging to fix each
> occurence of such a catastrophic failure.

Yes, changing all the Q-bus stuff just so you can use one brain-damaged
device would be a pain, and it seems so silly. Wouldn't it be a lot
simpler to make a small change to the RLV11 so that it only answers to one
address?  It can't be that bad.  The extra address lines aren't even
multiplexed with anything.  All you need is a few gates and at Q-bus
speeds it should be fairly easy to get it to work.

> This will probably make Q-bus graphics support especially difficult, as you
> have to be sure that none of your graphics buffers are over 256k long
> and that they are all aligned properly.

Well, the QDSS only wants 64k, so it wouldn't be a big problem.  OTOH, the
QVSS wants 256k and you wouldn't be able to use it with a RLV11.

> IMHO, the effort should be placed on fixing drivers that used to work
> in NetBSD until an "upgrade", such as the TSV05/TU80/TS11 class driver
> that was broken several years ago (for reasons that I don't understand,
> and I don't know how to get access to the several-year-old sources to
> figure out exactly what was broken.)

Yes.  Also, we need various improvements to babyVAX support.  Shared
libraries are also rather important for X and babyVAXen.
Supporting RL0x drives shouldn't be a priority. (...but of course if I
had some I'd probably go do it.  :-)

|  Boris Gjenero <bgjenero@undergrad.math.uwaterloo.ca>              |
|  Home page:  http://www.undergrad.math.uwaterloo.ca/~bgjenero/     |
|  "Luke, you're going to find that many of the truths we cling to   |
|  depend greatly on our own point of view." - Obi-Wan Kenobi, ROTJ  |