Balanced Technology Extended (BTX) Interface
Motherboard Volumetric Zones
Motherboard Primary Side Volumetric Zones and Motherboard Secondary Side Volumetric Zones define the footprint and height constraints that comprise the overall motherboard volumetric zones. All components in a BTX-compatible system must adhere to the motherboard volumetric zones according to the requirements in following table.
Table 3-3 Categories and Requirements for Motherboard Volumetric Zones
Category | Examples | Requirements |
Motherboard components | Memory modules, processors, rear panel motherboard connectors, and rigid portions of motherboard-terminated cable assemblies, component heatsinks, and components soldered to motherboard | Must fit completely within the motherboard volumetric zones (primary and secondary side) |
Chassis components | Chassis walls, chassis pan, motherboard mounting features, peripheral mounting brackets | Must not intersect the motherboard volumetric zone at any point. In addition, adequate clearance should be provided between the chassis, the motherboard volumetric and installed system components to avoid component interface and/or damage during shipping or other dynamic conditions |
Transition components | Add-in cards, air ducts, Thermal Module, SRM, flexible cabling from the motherboard to other system components, motherboard EMC grounding features | May cross the outer boundary of the motherboard volumetric zone. Some of these components, such as add-in cards, may have their own mechanical volumetric specifications which should be considered by the designer in addition to those specified in this document. The thermal module can reside across multiple zones (typically Zones A, C, F, G and H). The thermal module should not intersect the top boundaries of any of the volumetric zones |
Other System components | Disk drives, front panel cards, system power supply, and other system components not listed above | Must not intersect the motherboard volumetric zone at any point. In addition, adequate clearance should be provided between installed system components and the motherboard volumetric zone to avoid component interference and/or damage during shipping or other dynamic conditions |
Motherboard Primary Side Volumetric Zones
Motherboard primary side volumetric zones are defined in following figure. All areas are defined from the top surface of the motherboard.
Figure 3-3. Motherboard Primary Side Volumetric Zone
Motherboard Secondary Side Volumetric Zones
Motherboard secondary side volumetric zones are defined in following figure. All areas are defined from the bottom surface of the motherboard.
Also defined in the following figure are areas for inclusion of optional EMC features. If needed, EMC grounding features extending from the motherboard to the chassis should only be designed within these areas to ensure contact with the corresponding areas reserved in the chassis below the board for this purpose.
All zone boundaries are defined to avoid interface with components in the assembled condition. Additional clearances based on target assembly processes may need to be incorporated.