Performance of Running Code in External RAM

xinghua · ‎2009-08-04

Posted on August 04, 2009 at 10:15

xinghua · ‎2011-05-17

Posted on May 17, 2011 at 12:54

We are using High Density Series STM32 chip. The embedded SRAM is up to 64KB. We try running code from external SRAM, and it seems extremely ''slow''.

I am wondering how the performance will be like if running linux, considering normally linux kernel is large (over several hundred KBytes) and copied from a stroage device(flash) to RAM, and then wholly running in RAM.

ivanov-i · ‎2011-05-17

Posted on May 17, 2011 at 12:54

The external memory is not a good place for running a code for STM32. As AN2784 states the minimum access latency for the external memory is 3 cycles for half a word even if you put no delays in the configuration register (Figure 6).

In addition, the external memory is connected to D-bus, which means that there will be more delays waiting for data transfers over the same bus.