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External RAM doubts about size and speed

eng23
Senior

Hello,

My print size information from gcc shows:

 text    data     bss     dec     hex  filename

 196078     212   59184  255474   3e5f2  04-03.elf

The RAM usage is data + bss, in my case is: 59396 kB

But this value I think it is not true, because I'm using a display 480x272, so a single framebuffer uses more than this! (480*272*16 bits ~= 260kB)

I'm using external SDRAM, does gcc consider external sdram to print this value?

Another point, about the memory speed, I'm choosing the proper external RAM for my project and I see two options:

1- 64Mb (2M x 32) - In this case the access is through 32 bits and 143MHz

2- 64Mb (4M x 16) - 16 bits and 166MHz

Could this difference affect the display/graphics performance? A memory with 16 bits interface is a little cheaper, but I don't know if it worth it.

Regards.

Thanks.

5 REPLIES 5

Not clear what STM32 you are using but I would expect it to clock at 84, 90 or 108 MHz.

The linker will not track the use of pointers or constants defining addresses.​

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For that size of display you'd likely want to use 32-bit wide memory to allow for bandwidth for both you and the display to access the frame buffer. Do the math..​

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eng23
Senior

I'm using STM32F746 and 108MHz for SDRAM clock.

My question is because in STM32F746DISCO the external RAM is used in 16 bits and the performance is ok. I'm using TouchGFX...

I'd do the computations and benchmarking first, it is not a choice you can fix in software later. ​

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eng23
Senior

Thanks for the answers,

How can I determine the RAM usage in my project?

I'm using Atollic, TouchGFX and a external RAM.