Changes

Some applications require a quick boot time. When deploying an embedded Linux system, this time has to be evaluated in order to verify if it matches the system requirement, if any. Should the boot sequence is too long, several techniques can be used to speed it up. For more details, please see [[SDVX-TN-001:_Fast_boot_time|this page]] or [https://elinux.org/Boot_Time this article]. Generally speaking, it is worth to remember that '''different type of memories can lead to largely different boot times'''. A common scenario is the following:* The proof of concept (PoC) of a new product is developed using a microSD card as boot memory. Everything is stored there: bootloader, o.s. kernel, root file system, etc.*Then, the software is deployed onto the target according to the final production configuration by using SoM's onboard non-volatile memories. See [[Standalone_boot_(BELK/BXELK)#Use_case_.231|this real case]] as an example. Due to the fact that a large portion of the software is stored onto the NAND flash, the overall boot time may increase significantly. Why?**microSD card has a synchronous interface to the host, while raw NAND flashes used on DAVE Embedded Systems system-on-modules have not. Data communication between the system-on-chio (SoC) and the memory is much slower.**More importantly, raw NAND flashes are unmanaged memories. Unlike microSD cards, they don't embed a controller for handling the commands received from the host and taking care of low-level management of the underlying memory (which is based on NAND flash technology as well⁠). This includes but is not limited to wear leveling, bad blocks management, and read errors handling. In the case of raw NAND flashes, these tasks are all performed by the operating system running on the host processor.