8GB RAM Kernel Panic

[Snowhog]

Re: 8GB RAM Kernel Panic

As I've already provided in the previous post(s), PAE isn't incorporated into the -generic kernel. The -server kernel does have this support. Yes, your CPU supports PAE (as does dibl's and mine). But unless you recompile the -generic kernel with PAE support, or you install/use the -server kernel, you (as well as all the rest of us) will be limited to the 4G RAM limit imposed by the kernel.

[losmurfs]

Re: 8GB RAM Kernel Panic

I'm recompiling the kernel with:

...
# CONFIG_NOHIGHMEM is not set.
CONFIG_HIGHMEM64G=y
CONFIG_HIGHMEM=y
...

Everything set to ubuntu kernel defaults.

Ubuntu by default uses CONFIG_HIGHMEM4G=y meaning Ubuntu can use RAM above 1GB but not above 4GB, where CONFIG_HIGHMEM64G=y means that the kernel can use any amount of RAM all the way up to and including 64GB.

[losmurfs]

Re: 8GB RAM Kernel Panic

btw - snowhog - I already stated that before posting here I tried the server kernel too and the 64-bit -server kernel (sudo aptitude install linux-server, then rebooted, then from grub picked Ubuntu 7.10, kernel 2.6.22-14-server and then kernel panic, then rebooted and added mem=4000m, then I was able to boot.)

[losmurfs]

Re: 8GB RAM Kernel Panic

Anyone know of a good place for me to upload my new 64GB RAM capable kernel packages to in order to share them?

linux-image-2.6.22-14-intel-duo-64gb_2.6.22-14.47_amd64.deb
linux-headers-2.6.22-14-intel-duo-64gb_2.6.22-14.47_amd64.deb

I've only tested it on my home computer with 2GB, tomorrow I will return to work to test it on my workstation at work that has 8gb of ram.

[losmurfs]

Re: 8GB RAM Kernel Panic

FYI - It appears that both server and desktop kernels for ubuntu have:

CONFIG_HIGHMEM4G=y
CONFIG_HIGHMEM=y

Meaning that instead of being limited to 3.5GB they can use all 4GB if you have it, but you need:

CONFIG_HIGHMEM64G=y
CONFIG_HIGHMEM=y

to use more than 4GB. It is sad that when you have more than 4GB it crashes instead of just using the first 4GB like Windows XP (32-bit) does. The good thing is that you can use mem=4000m to run without taking the extra RAM out.

[Snowhog]

Re: 8GB RAM Kernel Panic

I agree. You would think that the kernel would include the support for 64GB of RAM by default, but include a test for both CPU support of PAE and system RAM over 4G before 'turning it on.' If the detected CPU didn't have PAE support, then simply limit kernel control of system RAM to the maximum 4G.

[losmurfs]

Re: 8GB RAM Kernel Panic

Good news everybody, perhaps the default generic kernel or the server kernel come with 64GB RAM support since I just compiled a new kernel and it still didn't work. So it may be an Intel bug, a Dell modification to keep people from using cheaper desktops instead of expensive servers, or a bug in the kernel. I have: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (is that the part of the chips et that controls memory addressing on the hardware side?) Anyways, still get a kernel panic in 2.6.22 compiled for >4gb, so now I am going to try 2.6.24, se if that works better.

[losmurfs]

Re: 8GB RAM Kernel Panic

Great news everybody, I just compiled the latest stable kernel with ubuntu default compile settings + I added config_highmem64g and config_highmem, and the result:

Kernel alive
kernel direct mapping tables up to 200000000 @ 8000 - 11000
PANIC: early exception rip ffffffff802781e1 error 0 cr2 16e0

My conclusion - my motherboard is designed for a max of 2x2gb or 4x1gb but not 4x2gb so I will just return 4gb to Kingston since they are the ones that said my Dell could use 8gb even though Dell my pc can only use 4gb. I guess Dell was right on this one.

[dibl]

Re: 8GB RAM Kernel Panic

Interesting -- thanks for letting us know how it came out.

Don't feel too bad -- I've been running with 4GB for a year, and I have not yet figured out how to actually get it all into use. Even doing audio file DSP processing maxes out my 2 CPU cores before the memory gets anywhere near fully utilized. Most of the apps are still 32-bit (or even 16-bit) and so they're not using the RAM that hard.