How to install Ubuntu on a laptop with soldered RAM module that has damaged cells
Note: For Ubuntu install help, please see here.
Note: Most high-end computer service shops can replace that defective 8G RAM chip(s) at minimal cost, and it would certainly be more reliable.
If you look in /etc/default/grub, you'll find a GRUB_BADRAM= parameter where you can identify what bad memory locations there are.
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
BADRAM setting in Grub2
The GRUB2 config file in Natty has a line for configuring kernel bad ram exclusions. So, I will assume that is the preferred way of mapping out a section of memory that is showing errors. The line I set was
GRUB_BADRAM="0x7DDF0000,0xffffc000"
The suggested way on every web site I could find was to set this was to run memtest86 and let it show you the BadRAM settings. memtest86 gave me a page of stuff I would have had to enter. I could see that all the addresses were in one 16K block, so I just wanted to map that 16K block out of action. Here is how I generated the correct entry.
The first parameter is easy. That is the base address of the bad memory. In my case, I could see that all the bad addresses were greater than 0x7DDF0000 and less than 0x7DDF4000. So, I took the beginning of the 16K block as my starting address.
The second parameter is a mask. You put 1s where the address range you want shares the same values and 0s where it will vary. This means you need to pick your address range such that only the low order bits vary. Looking at my address, the first part of the mask is easy. You want to start with 0xffff. For the next nibble, I will explain with bit maps. I want to range from 0000 to 0011. So, the mask for badram would be 1100 or a hex c. The last 3 nibbles need to be all 0s in the mask, since we want the entire range mapped out. So, we get a total result of 0xffffc000.
After setting this line in /etc/default/grub, I ran sudo update-grub and rebooted and my bad memory was no longer being used. No kernel patches are needed to map out bad memory using this method.
Source: https://help.ubuntu.com/community/BadRAM#BADRAM_setting_in_Grub2
Update #1:
If the system you are using already has (a) bad stick(s) of memory, you have two options: a) Put good memory in temporarily until you've built the patch b) If memory errors don't show up in lower memory, you can add the "mem=##MB" kernel option to temporarily disable memory above that point. Ex: According to memtest86, my stick of memory has errors between 315MB and 325MB. By adding "mem=314MB" I tell the kernel to pretend I only have 314MB. My system will be stable enough to build the patch, at which point I can pass a parameter to ONLY skip the section between 315MB and 325MB (this providing me 502MB of usable memory).
ie: Boot Ubuntu Live, at GRUB menu, hit e to enter edit mode, use the arrow keys to find "quiet splash", change to "quiet splash mem=2048MB", CTRL+x or F10 to continue booting.
Update #2:
To get memtest86, go to https://www.memtest86.com/ and download/run their free memtest to test your memory. Get at least one complete pass of all the 4/4 tests to confirm good memory. This may take many hours to complete.
Update #3:
Depending on WHERE your bad RAM is located, you might have a problem. Peter Cordes has a good idea. Remove the HDD. Put it into another computer. Install Ubuntu. Modify GRUB. Then return the HDD to the original laptop. Try and boot it.