Field-replaceable unit: Difference between revisions

Revision as of 14:35, 4 October 2011

Revision as of 14:47, 4 October 2011

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''This article is primarily about FRUs in computers.''

A '''Fieldfield Replaceablereplaceable Unitunit''' or ''('FRU''')<ref name="Newton16p364" /> is a [[circuit board]], part or assembly that can be quickly and easily removed from a [[personal computer]] or other piece of [[electronic equipment]], and replaced by the user or a technician without having to send the entire product or system to a repair facility. FRUs allow a technician lacking in-depth product knowledge to [[fault detection and isolation|fault isolate]] and replace faulty components.

==Computer Hardwarehardware==

A typical [[desktop computer]] is composed almost entirely of FRUs, including:

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Replacing an FRU while the machine is running is known as [[hot swapping]]. Support for hot swapping is mostly limited to [[high availability]] devices, power supplies, and cooling fans in systems having redundant ones.

To aid in fault isolation, a unit called a Fieldfield Replaceablereplaceable Unitunit IDentifieridentifier (FRU ID) holds the records of the devices that do not originally come with the baseboard or motherboard. Most (though not all) board manufacturers use EEPROM to store FRU IDs, which play a significant role in [[Intelligent Platform Management Interface|IPMI]]. The [[Baseboard Managementmanagement Controllercontroller|BMC]] contacts the FRU devices whenever there is a problem in the hardware to determine the device to replace. Most often, the BMC communicates with the FRU using the [[I²C]] bus protocol, but can also use other implementation-specific protocols.

==Other Equipmentequipment==

FRUs are not strictly confined to computers but are also part of many high-end, lower volume consumer and commercial products. For example, in military aviation, electronic components of [[line-replaceable unit]]s, typically known as shop-replaceable units (SRUs), are repaired at field-service [[Workshop#Backshop|backshop]]s, usually by a "remove and replace" repair procedure, with specialized repair performed at centralized depot or by the [[Original Equipmentequipment Manufacturermanufacturer|OEM]].

==History==

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Most [[transistor]]ized and [[integrated circuit]]-based computers had FRUs:

*Circuit boards containing discrete transistors and various passive components. Some examples:

**[[IBM]] [[Standard Modular System|IBM SMS cards]]

**[[DigitalSystem EquipmentBuilding CorporationBlocks|DEC]] [[System Building Blocks]] cards

**DEC [[Flip Chip (trademark)|DEC Flip-Chip]] cards

*Circuit boards containing monolithic ICs and/or [[hybrid circuit|hybrid ICs]]. Somesuch examples:as [[Solid Logic Technology|IBM SLT cards]].

**IBM [[Solid Logic Technology|SLT cards]]

**DEC [[Flip Chip (trademark)|Flip-Chip]] cards

Vacuum tubes themselves are usually FRUs.