ROM Code Boot Time Measurements

[AdrianGancev]

I want to share some measurements that we did in the office for the initial boot steps, from POR until user code is executed from DDR. Measurements were made with no HAB and don't include Power time, which is device dependent. They cover the following two steps:

• boot decision
• fetching of image into DDR.

Platform used: i.MX6Q / Sabre AI

Image Size	SD Class 4 on CPU CARD	NAND** on CPU CARD	Parallel NOR on CPU CARD
2KB	32 ms + 79* ms	25 ms	23 ms
166KB	40 ms + 79* ms	61 ms	56 ms
1MB	77 ms + 79* ms	247 ms	213 ms

* Constant value, measured only once (after SD card insert/platform power up), does not appear for subsequent s/w resets.

** Samsung K9G4G08U0M

Thanks to Andreas S. for help.

[mklug_xx]

Do you have measurements with HAB?

-Mike

[AdrianGancev]

When using HAB, RSA and SHA run in parallel. Here is an approximation based on measurements - add the following for HAB:

  If authenticated image < 1MB, a constant of 25ms. For i.MX6SoloX, that time could potentially be reduced to half.

  If authenticated image > 1MB, (Image_Size_MB / 1MB) * 25ms.