How to Pick a CPU When Buying Servers
As your IT team looks to upgrade your computational and enterprise storage systems, be sure you understand the choices and tradeoffs you face regarding your high-performance server CPU options. Some of our recommendations may seem, well, counterintuitive.
Fri, February 01, 2013
CIO — As 2013 rolls in and the economy stabilizes, many IT organizations are looking to upgrade their computational and storage systems. Like any IT purchasing decision, there are tradeoffs to consider and choices to make regarding hardware features and the technology available. When it comes to high performance computing, the first step is understanding your CPU options.
Intel vs. AMD
For at least this year, the two server CPU choices remain Intel and AMD. ARM might solve some of the computational parts of some of the problems, but in 2013, ARM won't have enough I/O bandwidth with 10 Gigabit Ethernet ports and storage to make it a viable alternative. This might change for 2014, but it's too soon to predict as development of PCIe buses with enough performance capability is complex.
The latest AMD CPUs have 16 cores, but only if you are running integer operations. When it comes to floating-point operations, you have only eight cores. This combined with the fact that the latest Intel server processors can read and write data from memory significantly faster on a per-core basis than AMD processors mean that AMD processors are best-suited for operations with low computational intensity and which do not require high memory bandwidth per core. .
Communications Between CPU Sockets
Another place that Intel has a major advantage is communications between CPU sockets. The current crop of Intel server CPUs support 25.6 gigabits per second (Gbps) of I/O bandwidth between CPU sockets over the Quick Path Interconnect (QPI).
This performance combined with the per-socket memory bandwidth performance exceeds the current performance of AMD CPUs. On multi-socket machines, this has a dramatic impact on the performance for all of the sockets because a process might be making a request for which memory has been allocated on another socket.
PCIe Bus Drives Intel Ahead
PCIe is where the rubber meets the road on why the latest Intel processors are far ahead of their AMD competitors. The Intel technology on the latest server CPUs runs PCIe 3 with 40 lanes on each CPU.
That means that the PCIe bus and the CPU are capable of 40Gbps of I/O bandwidth. This is far greater than the bandwidth of available on AMD processors. So if you need to do a lot of network I/O or disk I/O, PCIe 3 is the better choice because it has far higher bandwidth than PCI 2.0 and the performance of the bus will double, but also the Intel CPU supports more PCIe lanes.