DDR reported by /proc/iomem
 

I have intel x86_64 based system I am trying to understand /proc/iomem output. When i see cat /proc/iomem, along with many PCIe and other ranges of system memory i can see following

# cat /proc/iomem | grep -i ram

00001000-0009ffff : System RAM
00100000-cf3d8fff : System RAM
cf56e000-cf7fffff : System RAM
cf800000-cfffffff : RAM buffer
100000000-22dffffff : System RAM
22e000000-22fffffff : RAM buffer

My system has total DDR of 8GB
DDR_Size = 8*1024*1024*1024

Here is some calculation about total DDR memory reported by /proc/iomem

system_RAM_size = (0x0009ffff-0x00001000)+(0xcf3d8fff-0x00100000)+(0xcf7fffff-0xcf56e000)+(0x22dffffff-0x100000000)
RAM_buffer_size = (0xcfffffff-0xcf800000)+(0x22fffffff-0x22e000000)
RAM_Size = system_RAM_size+ RAM_buffer_size

but RAM_Size is not equal to DDR_Size, it is little less,
DDR_Size-RAM_Size=2056198

Would somebody please explain me why is it? Also what is the use of RAM Buffer? why is it separated from System RAM?
__________________

The Linux Hardware forum where you have your duplicate thread is the correct one to ask your question. And please review the comment already made by Rinndalir.

Duplicate threads are not helpful, please do not create repeats in alternate forums in your attempts to get an answer.