of PCI Express links provided by CPU board. Link repopulation is not a requirement in the specification, and must be implemented on the peripheral board with a PCI Express packet switch. PCIe/104 PCIe/104 is similar to the PCI/104-Express standard, but omits the legacy PCI bus to increase available space on the board (similar to the relationship between PC/104-Plus and PCI-104). The PCI Express connector location and pinout options the same as PCI/104-Express (both Type 1 and Type 2). Because the PCI bus connector is omitted, a PCIe/104 board is incompatible with PC/104-Plus and PCI-104 systems (unless a PCIe-to-PCI bridge device is used). Form factors The PC/104 Consortium's specifications cover three form factors which define the size and shape of the board. Each form factor may utilize one of the Bus Structures listed above. 104 or PC/104 The 104 Form Factor is defined to be , with mounting holes at all four corners of the board. The specifications also allow for a area beyond the edge of the PCB for I/O connectors. Some PC/104 products have oversized PCBs which extended into the I/O connector area. The extended PCB "wings" is not addressed in the specification, generally does not cause mechanical issues as long as the overall PCB + I/O connector overhang is within the maximum allowable dimensions of . The dimensions were originally defined in the PC/104 Specification, and as a result the form factor is still commonly referred to as "PC/104". The PCI/104-Express and PCIe/104 Specification introduced the "104" name to distinguish the form factor from the legacy PC/104 bus. EBX and EBX Express EBX (Embedded Board eXpandable) is a single board computer form factor, . The EBX form factor applies to the CPU board, but supports PC/104 form factor peripheral boards for expansion. The original EBX specifications allowed for the PC/104, PC/104-Plus, and PCI-104 buses. EBX Express adds the PCI-104/Express and PCIe/104 buses. EPIC and EPIC Express EPIC (Embedded Platform for Industrial Computing) is a single-board computer form factor which, like EBX, supports PC/104 peripheral boards but is smaller than EBX at . It allows I/O connections to be implemented as either pin headers or PC-style ("real world") connectors. The standard provides specific I/O zones to implement functions such as Ethernet, serial ports, digital and analog I/O, video, wireless, and various application-specific interfaces. EPIC Express adds PCI Express expandability. Stacking limits In general, every PC/104 stack will contain a