Chipset Platform: AMD 8100 (A8151 + A8131/8132 + A8111), Continued
The A8131 provides two PCI-X channels that correspond to PCI-X 2.0.
The A8131 or A8132 chips each provide two PCI-X buses. Because PCI-X is downwards compatible to PCI 2.2, the 64 bit wide slots can also be used for 32 bit expansion cards. Both chips work with 600 MHz, which reduces the total bandwidth of 2.4 GB/s in the A8132. The A8131, moreover, only works with 8 bits, which allows a maximum of 1.2 GB/s. The A8132 also supports PCI-X 2.0, which allows clock rates of 200 and 266 MHz for individual devices.
The A8111 controller is the I/O hub of the Opteron system.
Block diagram of the A8111 I/O hub.
The 8111 is comparable to the Southbridge of any desktop chipset. And here's why: the demand for bandwidth is also much lower. It won't come as a surprise, then, that this chip is connected by HyperTransport to the A8131 or the A8132 with only 8 bits and 200 MHz. This allows for 800 MB/s, i.e. enough for common applications.