2.9. F8 Chipset

The next evolution of HP system architecture design is the F8 chipset architecture, which is based on the ProFusion chipset. HP leveraged experience gained with the ProFusion eight-way architecture to develop the F8 eight-way multiprocessing architecture. The F8 architecture is shown in Figure 2-9.

Figure 2-9. F8 chipset.

HP developed the F8 chipset with a multiport, nonblocking crossbar switch to optimize efficiency and allow simultaneous access to memory, processor, and I/O subsystems.

The F8 chipset supports multiple PCI-X bridges and incorporates the HP embedded PCI Hot Plug controller for high availability in the I/O subsystem.

2.9.1 F8 Chipset Architecture

The F8 chipset was designed for even higher performance by optimizing the crossbar switch component and increasing bandwidths to match the processing power of the Intel Xeon MP processor.

The design includes a large buffer capable of holding 128 cache lines, 13 read ports, and 4 write ports

These features increase the number of concurrent transactions in the switch, and include a cache-coherency filter and a patent-pending Guaranteed Snoop Access algorithm to reduce the amount of cross-bus traffic. All of these features increase efficiency and improve the scalability of the F8 architecture.

For example, a bus operating at 100MHz and transferring four data packets on each clock would have 400MT/s (mega transfers per second).

The F8 chipset includes several innovations that provide high bandwidth, including scalable memory performance, PCI-X bridges, and Hot Plug RAID Memory.

2.9.1.1 SCALABLE MEMORY PERFORMANCE

HP engineers ensure scalable memory performance by increasing the memory bandwidths to an aggregate of 8.5GB/s, which is 33% more than the bandwidth of the processor buses combined. This design provides ample headroom for computing needs because each processor bus has four times the bandwidth of the Pentium III Xeon processor bus.

2.9.1.2 PCI-X BRIDGES

The F8 chipset can include up to four industry-standard dual PCI-X bridges in the I/O subsystem, each with embedded PCI Hot Plug controllers. Because each bridge can support two PCI-X bus segments operating at speeds up to 100MHz, the chipset can easily accommodate peripherals using high-speed interconnects, such as Gigabit Ethernet and Ultra320 SCSI.

2.9.1.3 HOT PLUG RAID MEMORY

Servers that enable Hot Plug RAID Memory use RAID DIMMs to provide fault tolerance and enable the hot replacement and the hot addition of memory when the server is operating. This eliminates unplanned downtime in the case of a DIMM failure.

When the memory controller in the F8 chipset needs to write data to memory, it splits the cache line of data into four blocks. Then each block is written, or striped, across four memory modules. A RAID engine calculates parity information, which is stored on a fifth cartridge dedicated to parity. With the four data cartridges and the parity cartridge, the data subsystem is redundant so that if the data from any DIMM is incorrect or any cartridge is removed, the data can be rebuilt from the remaining four cartridges.

2.9.2 F8 Chipset Advantages

When compared to a cache-coherent Non-Uniform Memory Access (cc-NUMA) architecture, the F8 symmetrical multiprocessor (SMP) architectures provide (1) a simpler programming model, (2) reduced average latencies overall, and (3) the ability to use standard operating systems and applications.

The F8 chipset from HP delivers these additional advantages:

• Eliminates potential bottlenecks by using very high bandwidths to match the processing power of the Xeon MP processor

• Eliminates potential bottlenecks using optimized crossbar switch capabilities

• Expands online replacement capabilities to include Hot Plug RAID Memory

The F8 chipset includes five memory controllers with HP Hot Plug RAID Memory and a multiported crossbar switch. The F8 chipset supports the following:

• 8.5GB/s of aggregate memory bandwidth

• 3.2GB/s of bandwidth for each processor bus

• 32GB of Hot Plug RAID Memory (40 DIMMs)

• Up to four 100MHz PCI-X bridges with hot-plug support

• Eight Pentium IV Xeon processors