[Ham-Computers] RAM PROBLEM

[nn6o]

Gene,

Dell shows the system will support upto 1GB of RAM using 2 @ 512MB DDR
modules.  The Crucial website shows 2GB is possible, but we'll go with Dell's
specs.

With that said, one possible factor is the memory density of the chips
themselves on the RAM module.  When the system was first manufactured, RAM
density per chip was lower than today.  For instance, to get the full 512MB on
one module might have required 16 chips (32MB each, 8 per side).  Newer
modules may be using higher density chips (e.g. 8 @ 64MB chips or 4 @ 128MB
chips).  If the max is indeed 1GB, then modules with 64MB or 128MB chips might
not be recognized by the 1150 as the memory controller can't access the higher
order address bits on each chip (and it would require 32 @ 32MB chips - not
enough space on an SO-DIMM module!).  If the max is 2GB, then 8 chip modules
should be OK, but not 4 chip modules.  Module organization is also a factor
(x16, x32, x64, etc), but doesn't seem as critical these days.  Both density
and organization might also be combined as a mitigating factor - perhaps the
system doesn't like certain module densities in certain organizations when
both modules are installed.

Another thought would be the module speed.  The 852GM chipset is spec'd for
100MHz or 133MHz modules (DDR200 and DDR266, respectively).  Faster 166/200MHz
(DDR333/400) are also available.  If you try to use a faster module, it should
work, but not always - it depends if the module can underclock reliably
(usually can).  More importantly, the modules also need to have the proper SPD
info the laptop is looking for.  The SPD is the module's identifier table and
it holds the various speeds and timings the module supports.  The SPD table
has 4 entries, but they may not all be filled in.  So, for example, if a
laptop wants a DDR266 module with 3-3-3-8 timings, it checks the module's SPD
entries to see if any of the entries meets this minimum spec.  If not, it
rejects the module and doesn't use it (for example, the SPD might support
DDR266, but at 4-4-4-12 timings).  Some "cheap" modules don't even have any
SPD entries - most "brand name" systems will reject these modules, but
"generic" systems might not care.

Whoops...just read Gene's post again and it looks like timing might not be a
factor as both modules work independently.  So, it could be module density
with organization, or possibly something about the laptop's memory controller
isn't able to support the total number of chips on both modules combined.
This isn't common on normally-clocked systems, but it is an issue with
"over-clocked" systems - the memory controller can't run at the overclocked
speed when all RAM slots of the motherboard are filled due to the extra
capacitance on the bus.  Not an issue here, but plausible if there is a
problem with the motherboard.  And, with that in mind, please see my open
reply to Jim Hill earlier about the Dell Inspiron 1150/5100/5160 series
laptops.


73,

  - Aaron, NN6O
    {nn6o}@arrl.net



-----Original Message-----
From: ham-computers-bounces at mailman.qth.net
[mailto:ham-computers-bounces at mailman.qth.net] On Behalf Of WØQFC
Sent: Sunday, June 24, 2012 4:50 PM
To: ham-computers at mailman.qth.net
Subject: [Ham-Computers] RAM PROBLEM

I have not run into this before and I need some help!

Computer is a Dell laptop Inspiron 1150.

It has two 512 MB sticks installed but the computer info shows that the
machine has only 512 MB total.

I can install either stick in either slot but it still shows only 512MB.

Any ideas?

Tks es 73

Gene, WØQFC