is DDR2 required for this processor to run Linux?

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mconover
Posts: 3
Joined: Wed Apr 01, 2015 8:08 pm

is DDR2 required for this processor to run Linux?

Wed Apr 01, 2015 8:18 pm

I bought the SAMA5D3 Xplained board in order to test software on it to see if it will work for my application. My only concern with using this processor and running linux is that the DDR2 is super expensive. So, is the DDR2 required to run linux or can I use a micro SD card to run linux on? I am going to start playing around with this board tonight, so I was wondering if the DDR2 is an integral part of this board. 

Thanks a lot,
Mike
blue_z
Location: USA
Posts: 1943
Joined: Thu Apr 19, 2007 10:15 pm

Re: is DDR2 required for this processor to run Linux?

Wed Apr 01, 2015 8:56 pm

mconover wrote:So, is the DDR2 required to run linux
The memory requirement is not just by Linux or any other OS. It is a fundamental processor architecture requirement that there is memory (aka main memory or RAM) to hold code and data for the CPU.
The integrated (to the SoC) RAM is only 128KB of SRAM, and too small to execute anything but a bootloader or test/demo programs.
For larger (standalone) programs (or an OS) external (relative to the SoC) memory is required.
mconover wrote: or can I use a micro SD card to run linux on?
No, that's "memory" that's attached as a peripheral and used as a storage device.
The processor architecture requires (in addition to main memory) a source of program code (since the type of main memory that is installed is volatile). A non-volatile storage device such as an SDcard is one such choice.
mconover wrote:I was wondering if the DDR2 is an integral part of this board.
Instead of wondering, you should read the board's specifications in the User Guide and other documentation (aka RTM or RTFM).
The DDR2 memory is already installed on the board.
It should only be removed or replaced with special equipment.


Regards
mconover
Posts: 3
Joined: Wed Apr 01, 2015 8:08 pm

Re: is DDR2 required for this processor to run Linux?

Wed Apr 01, 2015 10:41 pm

Thanks for the reply. My last question was just re iterating the first question. So, are you saying that I can use an SD card(not micro SD) in place of the 2 DDR2 chips? My only problem with this processor is that the 2 DDR2 chips cost $13 a piece, which is a show stopper for me. :( 
blue_z
Location: USA
Posts: 1943
Joined: Thu Apr 19, 2007 10:15 pm

Re: is DDR2 required for this processor to run Linux?

Thu Apr 02, 2015 2:09 am

mconover wrote:Thanks for the reply.
Then have the courtesy of actually reading and understanding it, rather than just skimming it and asking questions that have already been answered.
mconover wrote:So, are you saying that I can use an SD card(not micro SD) in place of the 2 DDR2 chips?
What part of "No, that's "memory" that's attached as a peripheral and used as a storage device" do you not understand?
BTW the docs indicate that there is no micro SDcard connector.
Also the SoC datasheet Errata lists the second interface as not usable for booting.
mconover wrote:My only problem with this processor is that the 2 DDR2 chips cost $13 a piece, which is a show stopper for me. :( 
What part of "The DDR2 memory is already installed on the board" do you not understand?
Or are you claiming that your board has the RAM removed?

IMO if you do not study the available documentation and just try to learn by doing, then you're looking at a rough, slow road ahead with frustration and failure.

Regards
mconover
Posts: 3
Joined: Wed Apr 01, 2015 8:08 pm

Re: is DDR2 required for this processor to run Linux?

Thu Apr 02, 2015 3:45 am

Thanks for being so nice and helpful!  :D

I misread your SD card comment that is why I asked again. 

I am designing my own circuit board with this processor on it. That is why I am worried about the cost of the DDR2. I know the DDR2 is already on the board. My board came with everything on it. lol I just didn't want to go down a path and waste a lot of time playing around with a processor/architecture that won't meet our cost target. I was just looking for an answer to a simple question. Of course, I will read all the documents before getting started. 
uCSimply
Posts: 11
Joined: Sat Oct 13, 2012 4:24 pm

Re: is DDR2 required for this processor to run Linux?

Fri Apr 03, 2015 1:02 pm

So good luck, man! :D

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