I was installing a new server with 8 gig RAM. (I’ll be using it as a vm box) After installation I did free and noticed that only 3.3 gig of physical RAM was found, hmm very strange. After talking to Bert he gave me a nice command I never heared off (dmidecode) . This gives you all kinds of hardware information. I was always using cat /proc/meminfo and free for my memory.
dmidecode displayed 2 x 2 gig. Hmm even odd, checked the invoice but it said 2 x 4 gig. They told me that it could be because I installed a 32 bit Linux. But I remembered reading in the Kernel book that Linux 32 bit could handle more. They had built something called HIGHMEM. But it seems that either the PAE or the HIGHMEM feature aren’t enabled by default. So after a reinstalling my box with a 64 bit Linux everything works fine.
Learned something again : if your box has more than 4 gig of memory, just choose 64 bit otherwise it’ll probably be wasted.
Didn’t know that command either, but I’ll remember it because it rocks 🙂
PAE support is available in 32 bit as well, you just need to compile kernel with highmem support and select 64G ram support option under:
Process Type and Features -> High memory Support.