On Mon, 10 Jan 2000, Michael L. Hitch wrote:

> On Tue, 11 Jan 2000, Simon Burge wrote:
> 
> > "Michael L. Hitch" wrote:
> > >   Mixing memory module sizes is not currently supported.  If a 32MB module
> > > is present, each memory slot occupies 32MB, and the 8MB modules will
> > > appear 4 times in the address space of each slot.
> > 
> > ISTR that Nx32MB + 1x8MB in that last occupied slot worked on the
> > 5000/2xx machines and it was the 5000/xx and 5000/1xx that had problems
> > with different sized SIMMS.  Is my memory(!) going bad?
> 
>   I'm fairly sure I verified that the 8MB module was seen in the entire
> 32MB address space on a 5000/260 and on a 5000/200.  I guess I'll
> have to test this again to be sure.  Having the 8MB module in the last
> occupied slot will appear to work until the kernel starts using the last
> 24MB of memory, at which time strange things will happen.
> 
>   My 5000/260 has 3x32MB modules, an empty slot, and then an 8MB module.
> A 'normal' kernel will just use the 95MB, but my experimental kernels will
> also use the additional 8MB.
> 
>   The 5000/xx doesn't appear to support mixed memory sizes, and I think I
> remember a 5000/1xx manual stating that memory modules had to be the same
> size.
> 
> --
> Michael L. Hitch			mhitch@montana.edu
> Computer Consultant
> Information Technology Center
> Montana State University	Bozeman, MT	USA
> 

 I seem to remember rreading from DEC documentation that the only
situation in which you were (supposed to) be able to have mixed memory was
when you had 14 32MB modules and then you could put an 8MB module in the
very last slot. 
 My 5000/240 came with 448 MB in 14 32MB modules and the 1MB Prestoserve
module in the last slot. I don't remember reading any scenarios about
mixing 32MB, 8MB, and the Prestoserve card; which leads me to believe that
it wasn't possible (at least under Ultrix). Is this a hardware limitation
or a software limitation? Good info for the DEC HW FAQ :-)
 As a side note, is there a way to test memory from NetBSD so that I could
target specific areas with a psuedo-random and/or sequential read/write
test? On one of my 5000/240 motherboards, the PROM RAM test checked out
all 360 some odd MB of RAM, I would boot and go into X, start a kernel
make and the system would panic with ECC errors. I did this a couple dozen
times and each time it was in a different address. I pulled the MB and
switched to another one which seems to be happily working. Is there such a
testing utilitiy available? Even if I couldn't test the first chip since
the OS is residing there, a Read/Write/Verify memory testing program would
be very nice to have.

	Chris