ohshaq :
what's the difference between a desktop & server CPU? If one is looking out for a HiDef gaming & Media PC, would a server process hold any advantage over desktop one? What is it that different in terms of functionality? Life expectancy, upgrade issues? Motherboard constraints?
I am trying to approach it from a performance/price/feature point of view. Not socket number, ect.
The differences between desktop and server CPUs:
1. Lifespan and duty cycle. Server CPUs are rated to run for longer periods of time at 100% sustained loads, whereas desktop parts are rated for less (although they will often run darn near forever.) I know AMD rates their Opterons for 5 years at 100% load 24/7 versus three years for the desktop chips.
2. Price. A server chip that is essentially identical to a desktop chip will cost somewhat more.
3. The ability to handle server-type platform features like error-correcting memory (although all of AMD's desktop CPUs with the possible exception of the Semprons have ECC support as well) and registered memory.
4. Some server chips can be run in multiple-CPU setups, whereas all desktop CPUs have been strictly single-CPU-only setups for quite a few years. They have this ability either through additional I/O links that desktop CPUs lack or have disabled.
5. Server CPUs frequently use different sockets than desktop CPUs. Server CPUs running in two-CPU setups sometimes use different sockets than desktop and server CPUs for four-CPU and higher servers always use different sockets than desktop.
6. Server CPUs frequently have more cores than desktop CPUs, since server workloads are much more multithreaded than most desktop workloads. AMD sells 8 and 12-core server CPUs and Intel sells 8-core server CPUs, while none of them sell more than 6-core CPUs for desktops.
Server motherboards are considerably different from desktop motherboards. Server motherboards are built for reliability and stability, not for flashiness. They use generic green PCBs with simple, unadorned heatsinks and have absolutely no overclocking options whatsoever. They almost all have a rudimentary onboard graphics chip that hangs off the PCI or PCIe bus rather than sitting in the northbridge. They also have serial ports, PS/2 ports, generally have at least two gigabit Ethernet ports, rarely have onboard sound, and frequently have only a couple of USB ports. They also frequently have many more RAM slots than desktop boards, multiple CPU sockets, SAS controllers, and are often larger than desktop boards. Oh, and they also cost quite a bit more than a desktop board that is otherwise similar.
Does anyone use a server cpu for such a platform? If not really... why?
My desktop has two Opteron server CPUs on a dual-processor motherboard. I got it because I do a lot of work with video and code compilation that loves a lot of cores. The two 8-core Opterons I have are considerably faster than even a $1000 Core i7 980X in just about every decently multithreaded task there is, but they cost about half the price of an i7 980X. I also greatly value stability and don't give a crap about overclocking and how flashy a board is, (it sits in a case with no window), so a server platform was a perfect fit for me. Oh, and I run Linux and any server hardware is basically assumed to be running that OS, so compatibility is a given.
mi1ez :
A server CPU has more error checking and would run games slower because of it. It would also cost more and (typically) require a server motherboard which would not be optimized for pushing pixels.
Error-correcting RAM has at most a couple percent overhead compared to non-ECC RAM. It does cost a little more since you need nine memory chips per side rather than eight with non-ECC RAM, but the cost difference is pretty slight. Registered memory must be what you are thinking of as registered memory is notably slower than unbuffered memory and it does usually cost a lot more. All registered memory sold today is ECC but not all ECC memory is registered. I have unbuffered ECC memory in my unit and it performs very similarly to typical unbuffered non-ECC desktop DDR3-1333.
endyen :
A bit of a history lesson but here goes.
Lots of people used socket 939 server chips in desktop mobos. They worked fine with non ECC ram.
Server chips are made on the same wafers as desktop chips. They are generally bined higher, and may get a different pinout.
I'm not sure if the current opterons will fit on desktop boards, but they probably do. They tend to make great overclockers, but at today's prices, they are not good value. (IMNSHO)
- Lots of people used Socket 939 Opterons in desktop motherboards since the Opterons overclocked better than the Athlon 64/A64 X2 chips. All of AMD's Athlon 64 and later CPUs support ECC memory, with the possible exception of Semprons. Anyway, ECC can be disabled or ignored, so putting unbuffered ECC memory in a system that does not support ECC memory will work; ECC will just be ignored. The 939 chips did not support
registered memory, and putting registered memory that the Opteron 200s and 800s took in a 939 board would result in the board failing to boot.
- Server chips share wafers with desktop chips up until a certain point in the wafer manufacture. There are a lot of steps in taking a wafer and making a finished chip and I was told at some point the wafer goes down a "server line" or a "desktop line." That could be early in the fab process if the server chip has wildly different features from the desktop chip or it could be finished wafers going to be binned and sorted down different lines. Some server CPUs use an entirely different die than desktop CPUs and thus are made from entirely different wafers, such as the Nehalem-EX's enormous 8-core die.
- The newest Opterons do not fit in desktop motherboards and cannot be overclocked on any existing motherboards. The 4- and 6-core Opteron 4100s use Socket C32 (LGA1207) and the 8- and 12-core Opteron 6100s use Socket G34 (LGA1944). The last Opterons that fit in desktop motherboards were the Opteron 1381, 1385, and 1389 "Suzuka" Opterons, which are analogous to the AM3 Phenom II X4s.
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