Bare metal application on Cyclone V too slow - DE10-Nano

First of all I'll make sure sdram access is cached.

Try to read bytes from sdram and extract the bit afterwards with something like this:

for(test = 0; test < 307200; test+= 8) {
   pixel8 = get8PixelLevels(test);
   for (bit = 0; bit<8; bit++) {
       test2 = pixel8 & 1;
       pixel8 >>= 1;
      }
}

If this way you experience a great improvement in speed, then the problem is with sdram access.

Hello Cris72,

Thanks for the answer but to check if it's running in the Cache I need to see the registers in a debug view? So, my getPixel function is similar to yours...another question do you have an email?

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Thanks for the answer but to check if it's running in the Cache I need to see the registers in a debug view?

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No. Debug view is not required. Just check if your execution time improves with this change

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So, my getPixel function is similar to yours.

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Nope. Your function returns a single pixel, mine 8. In an uncached system my code is faster, since the bottleneck is the number of sdram accesses.

Each sdram access involves a lot of delays (RAS, CAS, ...) while the bit extraction is made at cpu-register level.

In your case you make 7 out of 8 duplicate accesses to the same sdram address, so you lose a lot of time if the system is rather dumb and it accesses sdram every time as if it was a random address.

Actually I don't know how processor bus handles sdram access, that's why I suggest this simple code trick to verify if you have any improvement.

Do you compile with optimisations (-O2) ?

Does your preloader execute from flash and set the CPU to it nominal frequency ? (if you are using SDRAM then my guess is yes because you need a properly configured preloader to set up the SDRAM parameters). You should see a line like that from the preloader:

CLOCK: MPU clock 800 MHz