Cannot see both DIMMS on Dell DX0Q

[dbmcintosh]

Hi all...

I've recently installed Gentoo on a refurbished Dell DX0Q machine. All looking good so far (got X/openbox running now and all the apps I need) but unfortunately I cannot see all available memory, so it is a bit sluggish.

There are two DIMMS of 2GB but all I can see is less that 2 GB instead of 4GB. The BIOS thinks there is 4 GB and so does the dmidecode, but top and /proc/meminfo and conky all report less than 2GB.

I noticed they run at different speeds, but the BIOS is set to run at the 1066 (the lower speed), so from my forum browsing I believe this means that both should be accessible.

Anyone seen this before or have any suggestions on what the issue might be?

[NeddySeagoon]

dbmcintosh,

Post the part numbers of the two DIMMS and ideally the writing from the DIMM chips themselves.
Good clear photos on an image sharing site will do. I want to check that both DIMMS have the same geometry.

Also, swap them over. Many brain dead BIOSes run the RAM at the speed of the first stick of RAM read.
That's OK if its your slow stick detected first.

Boot into memtent86.
How much RAM does it see?
Run a few test cycles if it sees all 4G. If not, which 2G does it see, the fast or slow?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[dbmcintosh]

NeddySeagoon...

Thanks for this.

I was going to swap them over as you suggested but happened to read this blog https://www.parkytowers.me.uk/thin/wyse/d/dx0q/ about that very thing and decided to hold off. The guy had to do a bit of bodging (which I am happy to do if necessary), but I am not at that stage yet. The lower board is tricky to access and then difficult to remove the DIMM from, apparently.

Here is a picture of it though, for reference. The lower DIMM is just visible.

https://www.donaldmcintosh.net/content/dell-dx0q-memory-web.jpg

So, I moved from thinking it was an OS issue to it being a hardware issue, after getting your response. So - and I should have checked this before - I booted a second similar machine from boot USB today and found all memory running at same speed there and 4GB showing up. So, I just moved over the SDD drive this morning and now I can use the build I had but on 4GB hardware. I should have tried that earlier but for some reason thought it was an OS/BIOS/firmware thing I could maybe fix.

Once I've finished the build of the 4GB machine, I will return to the memory issue and try switching them around as you suggested.

Also, the part numbers you requested are on the original post btw under dcidecode output.

Thanks,
Donald

[NeddySeagoon]

dbmcintosh,

Your DIMMs are both 1 rank by 8 chips to get 2G. That's a start. I need the numbers off the top of the chips to check the geometry.

Geometry is a property of DRAMs dues to the way they are addressed. The address is applied in two parts, called the row address and column address. There is no need to have the same number of bits in a row as a column, so the geometry need not be 'square'.
In fact, it can only be square if the chip size is 2^n

Its a given that all the chips on the DRAM module have the same geometry but on two different sticks they may not.
The individual chips on your DIMMs are 256MB ... now it starts to get a bit tricky.

Some chip vendors sell imperfect chips smaller than they wore designed to be. That gets very very messy for the geometry.

Further, the memory controller in the CPU needs to know the geometry to drive the memory chips correctly.
Some memory controllers don't mind a mix, some do. Hence mixing memory modules can be a minefield.

memtest86 will provide some useful information. It does not need a HDD as it loads from the boot media in place of the kernel.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[dbmcintosh]

Apologies for the delay. Only got back to this today.

Here is a photo of both DIMMs now that I have been able to remove them.

https://www.donaldmcintosh.net/image/bothdimms-web.jpg

I'd still be interested to confirm they are both compatible but actually I think the lower one in the photo is possibly defective. When I switched them around the machine would not initialise at all. Not even to the BIOS. I had two spare DIMMS now that I knew worked so I switched these in the machine is now running with 4GB. ( A friend game me 2 x 4GB DIMMS laptop memory and these worked on a diff machine so I had then had to 2 x 2GB spare. )

Thanks,
Donald

[APolozov]

Your memory DIMMs have different numbers of chips, many motherboards (especially with SoDIMM memory) do not like this combination and want paired (identical) DIMMs. In extreme cases, DIMMs with the same number of chips are allowed.
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Excuse my bad English, I only study it.