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OMAP-L138 Boot Benchmarks

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Introduction

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

Host Boot Performance
Device Boot Mode Boot Time (ms)
1KB 124KB
C6748 NAND8 60
80
NAND16 36
52
NOR 3
15
SPI Flash 4
96
SD 34
195
SDHC 42
180
MMC 68
84
OMAP-L138
AM1808
NAND8 200
244
NAND16 144
203
NOR16 32
56
SPI Flash 36
312
SD 320
592
SDHC 336
544
MMC 264
460

Test Details

Methodology

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 

Software

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.

Hardware

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.

Hardware Part Number Frequency
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
45.6 MHz
SDHC Transcend 4GB Micro SD HC
38 MHz
SD Patriot 2GB SD
38 MHz
MMC palmOne 256MB MultiMediaCard
38 MHz


Discussion

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.