The IBM 7311 Model D11 I/O Drawer is designed for customers who require more than 24 I/O slots for the p5-570. The Model D11 is a rack mountable expansion cabinet that attaches to the IBM eServer p5-570 system. The Model D11 requires 4U of vertical rack space in a 19-inch rack. The Model 570 supports a maximum of 20 D11 drawers, which provides a maximum of 120 PCI-X adapter slots. Frontier offers refurbished D11 drawers. Call Frontier today or simply request a quote. 866-226-6344