Programmable architecture or the instruction set reminds us that the x86 is not the only instruction set, but one of many. Moreover, this set hasn’t got any standing in the sector of highest-performing servers as x86 systems used to lose to top-end RISC systems in performance and capabilities. They lose even today, although there have appeared many interesting and inexpensive solutions, as long as a RISC server can be called “inexpensive”, of course. In other words, x86 systems don’t occupy the apex of the performance Olympus.
Cost. Engineers may spurn the base metal, but the end customer does care about the price tag on the solution. Well, the very history of x86 systems bears witness to that: they were always losing in performance to all their competitors. But they always cost much less! And it is the x86 platform that survived, rather than the Next platform, for example, with its sparkling but very expensive hardware. No manufacturer of server systems ignores the price factor today.
Heat dissipation is a factor I have included on purpose. Of course, the purchaser of a 64-processor Sun Fire 15K machine can rest assured that however hot the processors may be, the server will cool them down efficiently. Thus, the absolute numbers of heat dissipation don’t matter much here. On the other hand, there are areas where heat becomes a suffocating factor for performance growth. For example, it is heat dissipation that puts restrictions on the number of CPUs in a blade server. By the way, blade servers are a peculiar market – performance proper is only a matter of third importance there, after heat dissipation and geometrical dimensions.
Availability is always important. Every server processor usually represents a compromise between the wishes of the engineering department and the capabilities of the manufacturing one. Considering that production output of server processors is always lower than that of desktop CPUs, the problem of availability of such solutions becomes critical. Moreover, chance sometimes gets involved into the manufacturing process: low yield of processors with desired frequencies and high percent of defective cores may make the manufacturer unable to produce the necessary amount of dies. Well, they sometimes can, but the cost becomes sky-high, hitting severely on the sales.
Anyway, in most cases, server manufacturers and developers handle the situation the right way and come up with ready products. In the next section we will try to discover what the performance of a server processor depends on.