Adding RAM to a Linux machine

[peterb]

I am running Red Hat Linux 9 on an Asus terminator fitted with 512Mb DDR RAM. The swapfile is 2Gbytes and runs in its own partition.

I tried adding an additional 512 Mb of DDR RAM (same spec, different mfr) and ran into problems. The system boots to the GRUB boot page, and then (usually) boots normally up to the "Checking module dependencies stage" when the system generates loads of messages and as often as not ends with a Kernel Panic, or a problem with init. Kernel is 2.4.18 with an initrd.

I have doubled memory on other linux systems (usually from 256 to 512 without problems.

Either memory stick on its own in either slot works without problem. My gusess is that the problem is that the memory is from different mfrs (although both the same speed). Is that likely to be the case, or am I missing something more subtle?

[Agent]

It shouldnt happen, but somtimes mixed RAM doesnt get on.
Install both sticks and run memtest (http://www.memtest86.com/) on them. If you get errors, there is your problem.
If you dont, you'll have to wait for the godlike linux guru's like Jo to arrive.

[directhex]

/me waves his hand

t'is a hardware problem

[Agent]

Oh, and make sure your motherboard BIOS is up to date.
A lot of memory problems can be solved by it

[chrestomanci]

I had a similar problem in my linux box about a year ago. I had two Crucial modules of different revs. When I called Crucial about it they replaced the older module with another of the same rev as my new one.

Crucial said that RAM modules can sometimes confilict. Is there any way you can get a matched pair for your system?

[peterb]

Yes - buy a new pair from scratch! I'll run the memtest this weekend, but your replies are confirming what I suspected! Anyone want to buy some DDR RAM?

[Agent]

If your mobo supports RAM voltage adjustment, drop another 0.1 ~ 0.2volts on the RAM. Can help if the RAM wants different voltages to each other

[chrestomanci]

Have you tried running the RAM at with more relaxed timings? Perhaps it would work reliably then?

[peterb]

Thnk you - haven't investigated the bios settings for the mobo - it hasn't been overclocked or tweaked. The bios is the latest (only) version.

I have noticed that Linux tends to be more demanding of hardware than windows - I did have cooling problems with the psu when I first built the machine.

Off to try the memory test now.

[peterb]

Update - Memtest went ballistic - never seen a screen fill up with red so quickly. Now to see if I can RMA it!

Edit

Full marks to Scan - they are taking it back!

[directhex]

Update - Memtest went ballistic - never seen a screen fill up with red so quickly.

/me waves his hand

t'is a hardware problem

[Agent]

Update - Memtest went ballistic - never seen a screen fill up with red so quickly. Now to see if I can RMA it!

Edit

Full marks to Scan - they are taking it back!

Was this on just the one stick, or 2 ?
If it was with them both in together, try them seperate. It could be an issue of the board not addressing the RAM correctly, and not the RAM being at fault itself !
Last thing you want is to be hit with a NFF fee.

[peterb]

I explained the problem to Scan, and said that although the RAM was probably OK, it was incompatible with the other stick, and they seemed happy. Think I'll get a couple of sticks of Corsair. (The mobo is an Asus ATX built into a terminator case.) Question now is whether to go for 2x512Mbyte or a single 1Gbyte stick.

Directhex...

[vaxen]

If you have a dual channel mobo, get a matched pair of 2x512MB. On a different note, you might want to install con kolivas 1GB lowmem patch for your kernel as it allows you to use the 1GB as lowmem and need not activate the highmem which causes overhead.

[Pedant]

I bought some generic ram from komplett once that just seemed to be incompatible with my motherboard - it ran okay in other computers, but that didn't help me out. Eventually had it exchanged for another stick.
Odd how two different sticks of RAM, both presumably within spec can not be happy running in the same system

[peterb]

Scan refunded the 512Mbyte in full (thank you) - so I bought a pair of Corsair TwinX 3200 - works like a dream!

Thanks to everyone for their input.