topic Are there any speed test/comparison fetching from different memories? in i.MX RT Crossover MCUs

Are there any speed test/comparison fetching from different memories?

EdSutter — Wed, 16 Mar 2022 14:26:15 GMT

I'm writing an application with hardware that has external spi flash essentially the same as the Teensy4.1. I'm running out of room on internal memory for text, so I'm moving some functions into xip-serial nor flash and now I'm noticing some of my realtime stuff is failing terribly. Is there any data that shows the performance hit between execution from ITCM vs OCRAM vs SDRAM vs XIP-serial-flash (or a subset thereof)?

Follow up question: Obviously the slowest interface is the xip-serial-flash, so is it reasonable to disable i-Cache on ITCM/OCRAM so that it is maximized on the external memories?

Thanks,

Re: Are there any speed test/comparison fetching from different memories?

jay_heng — Mon, 21 Mar 2022 09:00:41 GMT

Yes, you can refer to this post https://community.nxp.com/t5/RT-4-Digit-10xx-11xx-12xx/iMXRTxxxx-Memory-Performance-ITCM-DTCM-L1-CACHE-LMEM-CACHE-OCRAM/ta-p/1109993

I have also attached the pdf version in case you cannot access the post

Re: Are there any speed test/comparison fetching from different memories?

jay_heng — Mon, 21 Mar 2022 08:47:29 GMT

Cache can only boost OCRAM and external memory, no effect on TCM.

Disabling Cache on OCRAM may be helpful to external memory, but it is hard to quantize the effect.

Re: Are there any speed test/comparison fetching from different memories?

stephenschwartz — Thu, 28 Apr 2022 03:05:42 GMT

@jay_heng Tab 3 on page 14 'RT1176 - Cortex M4 core: Memory data throughput in MB/s' seems to be missing from the pdf. Would you be able to post that table? Thanks!