I think the call chain is like this main() (arch/x86/boot/main.c) calls detect_memory() (arch/x86/boot/memory.c) which calls detect_memory_xxxxx() functions, they invoke bios interrupts to determine the amount of RAM & fill the boot_params structure. Sudheer -----Original Message----- From: kernelnewbies-bounces@kernelnewbies.org on behalf of Arun S Sent: Thu 2/3/2011 10:18 AM To: kernelnewbies@kernelnewbies.org Subject: x86 memory detection Hi, How does the kernel detects the amount of available System RAM in the system under x86 architecture?. Under 2.6.x kernels, 1. Does it use BIOS interrupt 15 for determining the RAM OR 2. Does the boot loader fills the e820_map as explained inDocumentation/x86/boot.txt & Documentation/x86/zero-page.txt and the kernel uses in information OR 3. Is there any other mechanism (if so, in which file under kernel tree I can find this detection code) Thanks, Arun Please do not print this email unless it is absolutely necessary. The information contained in this electronic message and any attachments to this message are intended for the exclusive use of the addressee(s) and may contain proprietary, confidential or privileged information. If you are not the intended recipient, you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately and destroy all copies of this message and any attachments. WARNING: Computer viruses can be transmitted via email. The recipient should check this email and any attachments for the presence of viruses. The company accepts no liability for any damage caused by any virus transmitted by this email. www.wipro.com