OMAP-L138 Boot Benchmarks

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.