External RAM doubts about size and speed

[eng23]

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.

[Tesla DeLorean]

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.​

[Tesla DeLorean]

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..​

[eng23]

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...

[Tesla DeLorean]

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

[eng23]

Thanks for the answers,

How can I determine the RAM usage in my project?

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