HP A3639-69314 - Left PCI I/O backplane board - Has six PCI slots - N4000 left PCI I/O backplane board - Has six PCI slots - Mounts vertically in the left side of chassis Retail
HP A3639-69315 - Right PCI I/O backplane board - Has six PCI slots - N4000 right PCI I/O backplane board - Has six PCI slots - Mounts vertically in the right side of chassis Retail
HP A6144-69102 - PCI I/O backplane board - Has 12 PCI slots - L3000 PCI I/O backplane board - Has 12 PCI slots - Mounts vertically in the chassis Retail
HP A5191-69102 - PCI I/O backplane board - Has 12 PCI slots - L1000/L2000 PCI I/O backplane board - Has 12 PCI slots - in the chassis Retail