> From: der Mouse <mouse@Rodents.Montreal.QC.CA>
> Date: Sun, 9 Mar 2003 00:52:12 -0500 (EST)
> To: port-vax@netbsd.org
> Subject: Re: Observations on NetBSD VAX on old machines.....
> 
> >> (9M - that _is_ maxed-out for a KA630, right?).
> > Nope, max on a KA630 is 16M
> 
> Oh, cool!
> 
> Is it possible to have more than two RAM boards, or do RAM boards >4M
> exist?  I thought those were the limits, and those give 9M.  (Is there
> a limit at 16M?  I'd expect something like two 8M boards, or four 4M
> boards, either of which I would naïvely expect to give 17M.)

8M RAM boards exist.  The address-mapping circuit that is chained from
board to board maps out the 1M on the CPU board if there are two 8M
add-on boards.  As I recall, the memory board furthest from the CPU
gets addresses starting at 0,  the next one starts where the first
ended, and the on-CPU memory starts where that ended.  So if you
have two 8M boards the CPU memory gets mapped above 16M, which is
outside the address range of the KA630 architecture.

    carl
-- 
    carl lowenstein         marine physical lab     u.c. san diego
                                                 clowenst@ucsd.edu