# again a 4GB ram problem

## Gh0str1d3r

Hi,

I just updated my 64bit system (Core2 duo, kernel 2.6.29) to 4 GB ram. The whole ram is detected, but with more or equal 4GB in, network does not work. It fetches the ip address very slowly and ping even to the router is only sometimes possible with latency of some seconds!

With only one of the 2 2gb modules, everything works fine. I also recompiled the kernel. I did not find any option for HIGHMEM or like that, and as far as I understand other posts to that topic, on 64bit systems there should not be such a problem.

Any guesses what might help?

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## s4e8

enable CONFIG_GART_IOMMU or CONFIG_AMD_IOMMU, these two config will select the CONFIG_SWIOTLB, later is required for proper DMA operation.

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## Gh0str1d3r

All these points were already enabled.

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## s4e8

another posibility is the MTRR doesn't match to E820 memory range. please post your .config, lspci, dmesg and /proc/mtrr contents.

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## krinn

many newer motherbard have a security feature with ram.

As many ddr refuse to work without a certain voltage, default voltage will prevent them from working.

So the new feature is that (with some kind of magic) installing only 1 memory module in the motherboard make the memory work so you could enter the bios to setup your new voltage for your memory.

Once done, you could add the 2nd ram and all will be fine.

Also fastpath technology need 2 (or 3 for newer corei7) modules to be activate. So running with 1 module will disable it.

This could explain your problem with 2 module on and with only 1.

You should check your default memory voltage and that your bios fulfill their need.

You can also check fastpath problem by plugin the 2 modules but not in the bank couple. This is in your m/b manual, but generally it's 0101 (and the 2 linked ones are the same colors).

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## Gh0str1d3r

ok I think I found the problem: my mainboard doesnt really support that fast ram. I read the wrong line in the manual of my board, which was fsb and not ram speed  :Smile: 

But thanks for your help!

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## drescherjm

You should almost always be able to install faster ram than the motherboard officially supports, however you may have to run it at a lower speed. Also when you populate all slots of a motherboard in  some cases this means the memory will run at some reduced speed.

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## Gh0str1d3r

True, thats what it did. But I guess it was unstable because the optimal voltage of that ram was not supported by my boart (2.2 to 2.4 V, my board has max. 2.1 V)

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## Gh0str1d3r

Now I bought exactly the same RAM that was already in my pc. Network works with up to 3 gb in any slot / ram combination, but with 4 gb it doent. I also did a memtest which reported no errors. What could be the problem?

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## drescherjm

Try turning off memory hole remapping in your bios.

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## Gh0str1d3r

I dont find any option like this in my bios menu. Perhaps I should tell a little more about my hardware:

ASUS P5NSLI mainboard

4xMDT 1024 MB 667 MHz CL4 RAM

no overclocking, only defaultvalues in bios.

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## Gh0str1d3r

now I updated my bios, which did not solve the problem. I got a hint of a friend that it might have something to do with network buffer which should be at some point after the physical ram but is now in my ram. Is that possible and if yes how do I change that?

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## drescherjm

That is why I thought it was the memory remap. However I did download your motherboard manual and I could not find that feature.

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