External memory newbie question

leaf05 · ‎2015-03-07

Posted on March 08, 2015 at 00:19

Hi everyone, thanks for the time you�re taking for reading this.

I�m trying to make a small board that�s capable of running linux for testing purposes. There are for sale some system on modules (SOM) that seem quite reasonable using ST cortex M4 such as stm32f429 with 32MB external SDRAM.

After reading the datasheet I couldn�t figure out how much external memory can the stm32f429 handle. I want to run a full linux in the board and the more ram the better.

Please advice

Thanks a lot!,

Luis

#arm-cortex-m4

Tesla DeLorean · ‎2015-03-07

Posted on March 08, 2015 at 00:34

I want to run a full linux in the board and the more ram the better.

Absent an MMU that seems like a pointless exercise. Couldn't you find a more capable chip that runs at 500MHz-1GHz, has an MMU, cache and uses DDR(1/2/3) ?

I'm sure you could run the row/column/bank/width numbers for the F429, best possible case would be 2x 256MByte, of slow 90 MHz SDRAM, uncached, running code 6x slower than the CPU's internal memory.

So the question again is why?

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leaf05 · ‎2015-03-07

Posted on March 08, 2015 at 01:52

Hi Clive! thanks for your reply.

This is just for learning purposes, I´m trying to make a few labs for students at the university. We are starting from assembler, then C, and then some RTOS, ulinux and full linux. I want to use something different than the raspberry pi and beagleboard.

I wanted to know how to calculate how much ram can the stm32f429 manage so I can put a memory chip that suits my needs. I couldn´t find it in the datasheet.

Thanks a lot for your help

B.R.,

Luis