A compile farm is a server farm

Server farm

A server farm or server cluster is a collection of computer servers usually maintained by an enterprise to accomplish server needs far beyond the capability of one machine. Server farms often have backup servers, which can take over the function of primary servers in the event of a primary server...

, a collection of one or more servers

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

, which has been set up to compile computer programs remotely for various reasons. Uses of a compile farm include:

• Cross-platform development: When writing software that runs on multiple processor architectures and operating systems, it can be infeasible for each developer to have their own machine for each architecture — for example, one platform might have an expensive or obscure type of CPU. In this scenario, a compile farm is useful as a tool for developers to build and test their software on a shared server running the target OS and CPU. Compile farms may be preferable to cross-compilation
  Cross compiler
  A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is run. Cross compiler tools are used to generate executables for embedded system or multiple platforms. It is used to compile for a platform upon which it is not feasible to...
  
   as cross compilers are often complicated to configure, and in some cases compilation is only possible on the target, making cross-compilation impossible.
• Cross-platform continuous integration
  Continuous integration
  In software engineering, continuous integration implements continuous processes of applying quality control — small pieces of effort, applied frequently...
  
   testing: under this scenario, each server has a different processor architecture or runs a different operating system; scripts automatically build the latest version of a source tree from a version control repository. One of the difficulties of cross-platform development is that a programmer may unintentionally introduce an error that causes the software to stop functioning on a different CPU/OS platform from the one they are using. By using a cross-platform compile farm, such errors can be identified and fixed.
• Distributed compilation: Building software packages typically requires operations that can be run in parallel (for example, compiling individual source code files). By using a compile farm, these operations can be run in parallel on separate machines. An example of a program which can be used to do this is distcc
  Distcc
  In software development, distcc is a tool for speeding up compilation of source code by using distributed computing over a computer network. With the right configuration, distcc can dramatically reduce a project's compilation time ....
  
  .

One example of a compile farm was the service provided by SourceForge

SourceForge

SourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...

 until 2006. The SourceForge compile farm was composed of twelve machines of various computer architectures running a variety of operating systems, and was intended to allow developers to test and use their programs on a variety of platforms before releasing them to the public. After a power spike destroyed several of the machineshttp://sitedocs.sourceforge.net/status/support_cfstatus.html it became non-operational some time in 2006, and was officially discontinued https://sourceforge.net/forum/forum.php?forum_id=665363 on February 8, 2007.

Another example is the OpenSUSE Build Service

OpenSUSE Build Service

The Open Build Service is an open and complete distribution development platform designed to encourage developers to compile packages for multiple Linux distributions including openSUSE, Red Hat, Mandriva, Ubuntu, Fedora and Debian...

.