Editing Embedded system (section)

====Ready-made computer boards====
[[PC/104]] and PC/104+ are examples of standards for ready-made computer boards intended for small, low-volume embedded and ruggedized systems. These are mostly x86-based and often physically small compared to a standard PC, although still quite large compared to most simple (8/16-bit) embedded systems. They may use [[DOS]], [[FreeBSD]], [[Linux]], [[NetBSD]], [[OpenHarmony]] or an embedded [[real-time operating system]] (RTOS) such as [[MicroC/OS-II]], [[QNX]] or [[VxWorks]].

In certain applications, where small size or power efficiency are not primary concerns, the components used may be compatible with those used in general-purpose x86 personal computers. Boards such as the VIA [[EPIA]] range help to bridge the gap by being PC-compatible but highly integrated, physically smaller or have other attributes making them attractive to embedded engineers. The advantage of this approach is that low-cost commodity components may be used along with the same software development tools used for general software development. Systems built in this way are still regarded as embedded since they are integrated into larger devices and fulfill a single role. Examples of devices that may adopt this approach are [[automated teller machine]]s (ATM) and [[arcade machines]], which contain code specific to the application.

However, most ready-made embedded systems boards are not PC-centered and do not use the [[Industry Standard Architecture|ISA]] or [[Peripheral Component Interconnect|PCI]] busses. When a [[system-on-a-chip]] processor is involved, there may be little benefit to having a standardized bus connecting discrete components, and the environment for both hardware and software tools may be very different.

One common design style uses a small system module, perhaps the size of a business card, holding high density [[Ball grid array|BGA]] chips such as an [[ARM architecture|ARM]]-based [[system-on-a-chip]] processor and peripherals, external [[flash memory]] for storage, and [[DRAM]] for runtime memory. The module vendor will usually provide boot software and make sure there is a selection of operating systems, usually including [[Linux]] and some real-time choices. These modules can be manufactured in high volume, by organizations familiar with their specialized testing issues, and combined with much lower volume custom mainboards with application-specific external peripherals. Prominent examples of this approach include [[Arduino]] and [[Raspberry Pi]].