PCIe/104 Type 2 at first glance
Type 1, connector Bank 1 contains four PCI Express x1 links, 2 USB 2.0 ports, SMB, and some control signals. Bank 2 and Bank 3 contain only the PCI Express x16 link. In contrast, Type 2 maintains Bank 1 completely and maintains the same power, ground, and control signals on Banks 2 and 3 to ensure there will be no conflict with any existing PCI Express x1 or USB peripheral card.
Changing the PCI Express x16 link only affects PCI Express x16 peripheral cards and gives quite a few pins for Type 2. Bank 2 has PCI Express transmit signals, and Bank 3 has PCI Express receive signals. This convention, as well as all power and ground pins, was kept to ensure that there are no destructive consequences of improper stacking.
Type 2 adds two SATA ports to facilitate hard drives in the PC/104 stack. USB 3.0 caters to the future and is prominent in most companies’ road maps. Lane shifting on the SATA and USB 3.0 once again means universal peripheral boards. SATA and USB 3.0 are high-speed signals that require a connector with good signal integrity such as that offered by the PCIe/104 connector. LPC adds support for legacy devices, and many applications need a battery to back up the real-time clock. Two PCIe/104-compatible PCIe x4 links round out the connector. Table 1 shows the features and complementary nature of Type 1 and Type 2.
All peripheral boards using a PCI Express x1 link, PCI Express x4 link, or a USB 2.0 link on a PCIe/104 Type 1 bus will work on a Type 2 bus without changes to the existing peripherals. This allows peripheral module manufacturers to create one board that works on either bus.
Since Type 1 and Type 2 can be connected together mechanically, it is very important to note that neither board will be damaged if a card is inadvertently plugged into the wrong configuration. The bus is designed with the same power/ground connections and similar transmit/receive connections and will hold the host processor in Reset mode if incorrectly connected. Users can be confident that the boards from all manufacturers will play nicely together.
Host processors can have both connector pinout configurations on one board for additional functionality. For example, Type 1 on bottom and Type 2 on top will support a stack configuration from bottom up comprising power supply, PCI Express x16 video card, CPU, and SATA hard drive. To create compact, expandable SBC designs where PCI Express x16 is not required but the additional functionality of SATA, USB 3.0, and LPC is mandatory, a host can use Type 2 on top and bottom. This might be a useful configuration for embedded processors like Intel’s Atom. Just like Type 1, Type 2 provides mechanical backward compatibility and bridging to PCI-104, PC/104-Plus, and PC/104 modules.
PC/104 Consortium 916-270-2016 firstname.lastname@example.org www.pc104.org