Are there separate processors for servers?

To my knowledge a server PC and a desktop PC can have the same processor, but someone told me that servers are equipped with more powerful processors (that is these processor are designed for servers only). Is this true? Are there processors that are designed for servers?

Yes, this is true to an extent. From Intel, you have the Xeon line ( E3, E5 and E7 in the current labelling scheme). With AMD, you have Opterons.

The advantages of a server processor are usually:

• ECC memory support (checks and corrects RAM errors)
• Faster & more cores (eg. E3 roughly in the same league as i7 )
• Allows for more than one CPU per motherboard
• More RAM channels (and therefore slots), more & different chipset I/O

Some people say that these are also tested to run 24/7, but I think that regular desktop CPUs can also take that kind of abuse.

To my knowledge a server PC and a desktop PC an have the same processors.

Yes and no. Desktops PCs often have an AMD Athlon or an Intel Core CPU. Servers often use CPUs out of these families, but also some CPUs which you rarely find on a regular desktop. Some examples of CPUs families almost only used in servers are: SPARC, Itanium, Xeon, and Opteron ...

But someone told me servers are equipped with more powerful processors (that is these processor are designed for servers only). Is this true?

No.

There are processors which are designed for servers, but those are not always more powerful. E.g. sometimes you want a low power CPU which does not need to be fast, but which needs to fit in a server grade motherboard, or needs higher reliability. (Practical example: a domain controller in a data centre. Low power usage and low heat production are quite important in data centres)

Are there processors that are designed for servers?

Yes. See the examples above.

These CPUs usually have a few extra features which are often not found on desktop class CPUs, such as ECC memory support.

I explicitly write often, bacause this is not always the case. E.g. the desktop I am typing from has consumer grade motherboard aimed at overclockers. However I can replace the current Core i7 i920 (a desktop class CPU) with a Xeon (server class CPU) and gain ECC. However this feature is not important enough for most home users and the models supporting this are usually more expensive.

There are most certainly processors you would (probably) never need on a desktop computer. I don't see any reason for you to be rocking away on four 8-core processors, your programs wouldn't even know how to use them. You might also need specific equipment to run these processors. Then of course there's different features for every piece of equipment that you may or may not need to run your server.

It's not so much a 'server vs desktop' question as it is a question of practicality. My desktop is far more powerful than many of the servers I use, but has nowhere near the capacity the virtualization servers do at my work.

Really it's just a matter of what you want. I can't say I would mind having 64gb of RAM + 32 cores for an absolutely massive sandbox. So for many the line between 'desktop' and 'server' might get blurry. Think practically and not in genres.

Intel have a lot of processors dedicated for server usage:

http://www.intel.com/cd/channel/reseller/apac/eng/products/server/processors/index.htm

AMD has the server family as well:

http://www.amd.com/us/products/server/processors/pages/server-processors.aspx

High-end Servers running on Solaris OS use SPARC processors

There's two ways of looking at your question.

1) Are there chips that are pretty much just used in servers?

Yes. Intel's Itanium is one, IBM's POWER, Sun/Oracle's SPARC, are others. HP Used to have PA-RISC, but they dropped this and invested in Itanium. I even had a Motorola 88000 desktop for a while.

Sometimes "server" chips become more mainstream. When new and expensive, the Motorola 68000 was a server chip, powering early versions of SunOS/Solaris, HP/UX and others. It them moved to desktops (the Mac, the Amiga, etc) and now is so cheap to be an embedded controller. The MIPS chip followed much the same path, starting as SGIs server chip, now used in game machines mostly

These tend to be physically bigger than normal chips (the Itanium housing is a brick) and has some high end features, like ECC, tend to be have hot swappable components, etc. These are more expensive, and tend to draw a lot of power (so laptops are out). These are not Intel x86 compatible, you'd need code specifically compiled for the chip.

2) Are there Intel x86 compatible chips that are server chips?

Yes. Intel's XEON series was a server play. They were based on their standard desktop chips, but with some enhancements. At a minimum they have more cache to be faster, but also some other changes like ECC memory compatibility, or slight microcode differences. Sometimes they'd clock higher, or have