[NTLUG:Discuss] OT:strange memory activity

[Kelledin]

On Friday 12 March 2004 09:50 pm, Wayne Dahl wrote:
> This is way off topic for a Linux list, but with so many
> computer geeks on here, I can't resist asking.  My
> mother-in-law inherited an old computer from us and when
> upgrading memory on it, something strange happens.  It's an
> Intel P-II 366.  When she wanted to install AOL 8.0 on it, I
> had to upgrade the memory from 32M to 64M.  Figuring I would
> stave off future memory needs, I bought a 128M stick from
> Fry's and installed it.
>
> The computer came back up seeing only 64 Megs of memory.  I
> thought maybe it was either a bad stick or was possibly a 64
> Meg stick packaged in a 128 Meg blister pack.  At any rate, it
> was enough to install the software, so I let it go.

At this point, I would think perhaps it's an issue with 
double-sided DIMMs--i.e. you have a double-sided DIMM, but the 
motherboard refuses to recognize both sides in a single DIMM 
slot.

> Now she wants to upgrade to AOL 9.0 and it requires 128 Megs
> of memory, so I had her buy a 256 Meg stick, which she got
> from Office Depot, I think.  Before I installed that memory, I
> saw her computer was now seeing 128 Megs of memory instead of
> the 64 it was seeing before. Sometime since I installed that
> stick, the computer magically started seeing it for what it
> was.
>
> Being the idiot I am, instead of just installing the 
> software for her, I added the 256 Meg stick and restarted the
> machine.  It still only saw 128 Megs.
>
> Ok, possible bad stick, right?  Wrong.  I took out the 128 Meg
> stick, installed the 256 in the same slot thinking the other
> slot might have been bad, and the machine only saw 64 Megs. 
> Uh oh.  I installed the 128 Meg stick back in, now IT shows
> only as 64 Megs.  After I pulled that stick out, no matter
> which stick I put in there, 1 or both, all it sees is 64 Megs.
>  Now, I'm thinking that since it magically started seeing the
> other 64 Megs of that 128 Meg stick on its own, it might do it
> again, although I'm not holding out any hope.  So far, it
> still only sees the 64 Megs.

Now it sounds like maybe the system just doesn't want to 
recognize more than 64MB per slot?  I'm starting to wish I had 
the motherboard manual handy, so I could look through it to see 
supported memory configurations.  In any event, it sounds like 
it bears an old i440LX chipset, or possibly the cheaper i440EX 
variant.  It might be an i440BX, but I doubt it.

A lot of times, if you exceed the "supported" memory 
configurations for a motherboard, you'll get odd intermittent 
problems--i.e. if you use unbuffered memory when you really need 
registered memory, you could easily end up with frequent 
blue-screens or memtest failures.  This could be such an oddball 
case.

The i440LX chipset supports up to 1GB of PC66 (a fully-assembled 
i440LX motherboard may support less than that).  The i440EX 
chipset only supports 256MB rather than the full 1GB.  In either 
case, if the motherboard supports 256MB DIMMs at all, it likely 
only supports them in registered DIMMs.

Generally you can determine the chipset type by reading the POST 
or BIOS screen, or reading the markings on the chipset's 
Northbridge (a 1"x1" solder-mounted chip usually located between 
the CPU and the DIMM slots).  Beware that some Northbridges are 
covered by small heatsinks that probably shouldn't be messed 
with.

> Any ideas about what might cause this?  Would a BIOS upgrade
> (assuming one is available) help?  I have gone into CMOS setup
> and can't find anything in there to make the system recognize
> the added memory.

A BIOS upgrade is worth a shot.  Just use memtest86 make sure 
your RAM configuration is stable first; it would be a shame for 
a RAM error to crash the system in mid-BIOS-flash!

-- 
Kelledin
"If a server crashes in a server farm and no one pings it, does 
it still cost four figures to fix?"