OMAP-L138 Boot Benchmarks
This page gives measurements of the boot times for various boot modes supported by OMAP-L138/AM1808/C6748 and derivatives. Although the number can be considered typical, they only apply to the exact environment used for the benchmarking.
Host Boot Performance
|Device||Boot Mode||Boot Time (ms)|
|SPI Flash|| 4
|SPI Flash|| 36
The test case used immediately toggles a GPIO at the start of the main function. Boot times were measured from the rising edge of RESETn to the falling edge of the GPIO.
The board begins in a powered state to remove variability of power-up times. For example, some MMC/SD cards can take up to 1 second after power is applied to be accessible.
Two images sizes were used:
- The 1KB image size boot time basically represents the initialization time to read any data from the device.
- The 124KB image size shows how long it takes to boot a larger image
The following formula can be used to estimate boot times (time_x) for other image sizes (size_x):
time_x = time_1kb + size_x * (time_124kb - time_1kb) / 123
The test case is loaded completely into L3 shared memory, so no external memory is used. The bootloader enables the PLLs and the host CPU runs at 456 MHz.
Testing was performing on Revision 2.1 of OMAP-L138/AM1808/C6748 devices. Boot times may differ greatly from previous revisions for some boot modes.
|Board||LogicPD OMAP-L138 EVM||-|
|SoC||OMAP-L138/AM1808/C6748 Rev. 2.1||456 MHz|
|NAND8||Micron MT29F4G08AAC 8-bit NAND Flash||-|
|NOR||Intel PC28F640P30T85 16-bit NOR Flash||-|
|SPI Flash|| Winbond W25X64VSFIG 64M Serial Flash
|SDHC|| Transcend 4GB Micro SD HC
|SD|| Patriot 2GB SD
|MMC|| palmOne 256MB MultiMediaCard
The results show that the OMAP-L138/AM1808 boot times (ARM boot devices) are generally much longer than for the C6748 (DSP boot device). There are a few explanations for this:
- The ARM cache is not enabled by default, while the DSP cache is. This means that the code, especially delay loops, will execute much faster on the DSP.
- The OMAP-L138/AM1808 require additional time before the ARM bootloader begins executing.
- The DSP compiler generates fewer instructions for delay loops than the ARM compiler, resulting in faster execution.
For larger boot images on OMAP-L138/AM1808, it would be beneficial to enable the cache through AIS commands. Future versions of AISgen will provide this option.