Pci Express Pinouts Description For Single-Slot Socket Direct Card - Nvidia MCX651105A-EDAT User Manual

PCI Express Pinouts Description for Single-Slot Socket Direct Card

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This section applies to ConnectX-6 single-slot cards (MCX653105A-EFAT and MCX653106A-EFAT).
ConnectX-6 single-slot Socket Direct cards offer improved performance to dual-socket servers by enabling direct access from each CPU in a dual-socket
server to the network through its dedicated PCIe interface. The PCIe x16 interface is split into two PCIe x8 in a row, such that each of the PCIe x8 lanes
can be connected to a dedicated CPU in a dual-socket server. In such a configuration, Socket Direct brings lower latency and lower CPU utilization as the
direct connection from each CPU to the network means the Interconnect can bypass a QPI (UPI) and the other CPU, optimizing performance and improving
latency. CPU utilization is improved as each CPU handles only its own traffic and not traffic from the other CPU.
In order to allow this capability, a system with a special PCI Express x16 slot is required. Table 31 provides the pin definitions of the required four special
PCIe pins.
PCIe
pin#
B82 1Kohm pull up to 3.3VAUX
A32 P signal of differential PCIe clock (100MHz nominally) of the CPU which connects to PCIe lanes
15-8 of the PCIe connector
A33 N signal of differential PCIe clock (100MHz nominally) of the CPU which connects to PCIe lanes
15-8 of the PCIe connector
A50 PERST signal from the CPU which connects to PCIe lanes 15-8 of the PCIe connector
Server Connection for 2x PCIe x8 mode Server Connection for 1x
PCIe x16 mode
Either leave unconnected or Configure the card to work at 2x PCIe x8 or 1x
pulled to GND PCIe x16 modes
Not Connected
Not Connected
PCIe clock for ConnectX-6 PCIe bus lanes [15:8]
Not Connected PERST (PCIe Reset) for ConnectX-6 PCIe bus
lanes [15:8]
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