This optional expansion module provides IBM eServer BladeCenter T with the capability to support legacy telecommunications network interfaces, including T1/E1/J1, SS7, ATM and ipSEC connectivity. Each module, which supports two 100MHz PCI-X adapters, attaches to either an HS20 or HS40 blade and consumes one of the eight blade slots available in the BladeCenter T chassis. As a result, a PCI I/O expansion unit integrated with an HS20 blade creates a doublewide blade solution and a PCI I/O expansion unit integrated with an HS40 blade uses three blade slots. A second module may be deployed for redundancy within the BladeCenter T chassis or to support two additional network interfaces (via PCI adapters) non-redundantly. This option provides service providers with the flexibility to easily attach to and support many different types of networks (voice, data/IP).