The Standard Performance Evaluation Corporation. A non-profit corporation which makes benchmarks for various computery tasks - who's got the fastest web server? Whose filesystem is more efficient? Their tests are to be taken more seriously than things like Netbench or Winstone, as they have a very stringent set of requirements for publishing the results. They provide source code with each of their benchmarks for more transparency. The test with which I am familiar is System File Server (SFS, formerly known as LADDIS).

write-up is a person because in the US, corporations are legally people - nutty, huh?

Spec can be short for specification of for speculation.

To build on spec can mean built to specifications, to meet a specific demand. This sense is often used in manufacturing. It can also mean built on the speculation (hope) that someone will want to buy it – this sense is used in real estate.

'Spec' might be considered an contronym.