Aside from the rpi-update option, there seems to another (possible) reason why the reported memory is less. This time its to do with the kernel space / user space memory splits. This post details the fix which involves tweaking the kernel build configuration and rebuilding it from the source code. One user reported success

by tesla01 » Thu Feb 05, 2015 8:04 pm Hi, I confirm that the 2G/2G option works when use custom kernel

Feb 5 19:17:12 raspberrypi kernel: [ 0.000000] Memory: 940776K/966656K available (5785K kernel code, 377K rwdata, 1760K rodata, 396K init, 771K bss, 25880K reserved)

Thanks :)

You will need to verify this is indeed the cause (by checking the value of CONFIG_VMSPLIT is either CONFIG_VMSPLIT=3G or CONFIG_VMSPLIT=2G) as some posts further down in that link report success like so

by birdman » Thu Feb 12, 2015 10:01 pm Just this minute had an update to libraspberrypi-* and raspberrypi-bootloader. kernel now 3.18.7-v7+. memory now reported by top as "KiB Mem: 998096"

Thanks!!

while some others didnt have the same results

Unfortunately I am not near my PI to verify any of these claims.

Aside from the rpi-update option, there seems to another (possible) reason why the reported memory is less. This time its to do with the kernel space / user space memory splits. This post details the fix which involves tweaking the kernel build configuration and rebuilding it from the source code. One user reported success

by tesla01 » Thu Feb 05, 2015 8:04 pm Hi, I confirm that the 2G/2G option works when use custom kernel

Feb 5 19:17:12 raspberrypi kernel: [ 0.000000] Memory: 940776K/966656K available (5785K kernel code, 377K rwdata, 1760K rodata, 396K init, 771K bss, 25880K reserved)

Thanks :)

You will need to verify this is indeed the cause (by checking the value of CONFIG_VMSPLIT is either CONFIG_VMSPLIT=3G or CONFIG_VMSPLIT=2G) as some posts further down in that link report success like so

by birdman » Thu Feb 12, 2015 10:01 pm Just this minute had an update to libraspberrypi-* and raspberrypi-bootloader. kernel now 3.18.7-v7+. memory now reported by top as "KiB Mem: 998096"

Thanks!!

while some others didnt have the same results

Unfortunately I am not near my PI to verify any of these claims.

This question is probably a duplicate of this

Linked from this discussion is this post, at the end of which it is explained that the available (accessible) memory has been reduced for compatibility for certain softwares (sonic pi)

The current rpi-update kernel does have the full 1G supported (but breaks sonic pi). That will become the "stable" kernel in the future when we have a solution for the sonic pi problem.

So, the full 1G of sdram will be available in the future when we believe it's stable for use uses. If you want it now, then run rpi-update, but be aware that sonic pi (and possibly other apps) may break.

Aside from the rpi-update option, there seems to another (possible) reason why the reported memory is less. This time its to do with the kernel space / user space memory splits. This post details the fix which involves tweaking the kernel build configuration and rebuilding it from the source code. One user reported success

by tesla01 » Thu Feb 05, 2015 8:04 pm Hi, I confirm that the 2G/2G option works when use custom kernel

Feb 5 19:17:12 raspberrypi kernel: [ 0.000000] Memory: 940776K/966656K available (5785K kernel code, 377K rwdata, 1760K rodata, 396K init, 771K bss, 25880K reserved)

Thanks :)

You will need to verify this is indeed the cause (by checking the value of CONFIG_VMSPLIT is either CONFIG_VMSPLIT=3G or CONFIG_VMSPLIT=2G) as some posts further down in that link report success like so

by birdman » Thu Feb 12, 2015 10:01 pm Just this minute had an update to libraspberrypi-* and raspberrypi-bootloader. kernel now 3.18.7-v7+. memory now reported by top as "KiB Mem: 998096"

Thanks!!

while some others didnt have the same results

Unfortunately I am not near my PI to verify any of these claims.