On Thu, 16 Nov 2000, Paul Whittaker wrote:

> > [snip] To my knowledge there is no way to
> > tell which memory module is which, as they don't carry anything but the DEC
> > 54xxxx... part number. Easiest thing to do is cnfg 3 and it'll tell you what
> > size the modules are. (Have to be all 8 or all 32, no intermixing [yet].)
> 
> The "cnfg 3" command will only show what the PROM believes is present,
> which may not match reality if someone has been fiddling.

	OK, define fiddling. Desoldering SMT ram chips and replacing them 
with smaller capacity/higher speed ones? I have yet to see the PROM be
wrong on any of the four DECstations I have. 
 
> You can determine the capacity of the SIMM from the access speed of the
> memory chips on it.  If they are 100ns (chip ID ends in "-10") then it's
> an 8Mb SIMM.  If they are 80ns or 70ns (chip ID ends in "-80" or "-70")
> then it's a 32Mb SIMM.  There are also different DEC part numbers,
> (A01... vs A02...) but the part number is on a sticker and on occasion I
> have found some mislabelled 32 Mb SIMMs, so I wouldn't trust these.

	You might as well just say that you can tell how large the module
is by the number of chips on it! There have been probably four revisions
of these modules. I wouldn't count on RAM speed being an identifying
factor personally, but that's just me. All the Axx numbers are masked on
the module itself, every module I've looked at has the same number 8MB and
32MB alike. I haven't found MS-02 xx anywhere. I think Axx is the
revision of the board itself, but I could be wrong.

> The rule with intermixing 32 Mb and 8 Mb SIMMs is that if 32 Mb SIMMs
> are present then only a sinlge 8 Mb SIMM may be fitted, and only in the
> highest slot number (14).  As far as I am aware this is a
> hardware/firmware limitation and nothing to do with the O/S you are
> running.

	Someone here was working on a kernel that could use intermixed
modules, so I think it's an OS issue with address space. Where 8MB and
32MB modules use the same address space. It wouldn't be that hard to
figure out if you have an 8MB module and tell the kernel how to map it
appropriately IMHO, but I'm not a programmer yet.


	Chris