dcollet1
Posts: 2
Joined: Tue Dec 11, 2012 8:53 pm

Comparing memory beween 256k and 512k board

Wed Dec 12, 2012 1:17 am

I used am trying to verify the different available memory between the older B board with 256mb RAM and the new 'b' revision board with 512mb... I am using the same 2012-10-28-wheezy-raspbian image...
I used top to view to identify system memory

top - 20:10:35 up 2:24, 2 users, load average: 1.02, 0.82, 0.63
Tasks: 89 total, 1 running, 88 sleeping, 0 stopped, 0 zombie
%Cpu(s): 1.7 us, 1.7 sy, 0.0 ni, 96.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 189104 total, 164028 used, 25076 free, 19484 buffers
KiB Swap: 102396 total, 0 used, 102396 free, 57200 cached

If I interpret this correctly, it shows a total memory size of 189.1mb... I get the same results with either board.
Is there a different command that will show the actual memory available as close to 512mb?

dcollet1
Posts: 2
Joined: Tue Dec 11, 2012 8:53 pm

Re: Comparing memory beween 256k and 512k board

Wed Dec 12, 2012 5:09 am

After posting my original comment and question, I created a new Linux image on another SD card. I then configured it on the 512mb board. Once I completed the configuration process and rebooted, I ran top. It now recognizes 448996kb RAM. lshw also reports 438mb memory.

So, this leads me to believe that the Linux image will attempt to allocate as much memory as is available when you initially configure the SD card on the Raspberry Pi board. It senses the available memory of the board you installed it on and partitions memory accordingly. If you move the SD image to another board, with more RAM, it will not recognize or make that additional memory space available automatically.

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Mursili
Posts: 28
Joined: Fri Nov 23, 2012 2:12 am

Re: Comparing memory beween 256k and 512k board

Wed Dec 12, 2012 6:02 am

...and I find that it does things in quite the opposite order...

When I put the SD card from my rev. 1 Pi into the rev. 2 Pi, it shows much more than 256MB free memory. This implies that it is keeping a constant amount of GPU memory. I do not know if this is right or wrong at this time.

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Dweeber
Posts: 606
Joined: Fri Aug 17, 2012 3:35 am
Location: Mesa, AZ
Contact: Website

Re: Comparing memory beween 256k and 512k board

Wed Dec 12, 2012 6:12 am

In the newer versions of Raspian..... memory is allocated to the GPU by added (not included by default) the settings:

gpu_mem_256=XX
gpu_mem_512=XX

If you have a 256mb board, it will follow the gpu_mem_256 entry, 512mb the gpu_mem_512 entry.

You can allocate as little as 16

Ref:
http://elinux.org/RPiconfig#Memory

The default memory allocated to the GPU with no configuration entries is 64
Dweeber A.K.A. Kevin...
My RPI Info Pages including Current Setup - http://rpi.tnet.com

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