IBM's new transactional memory

Up until now, transactional memory research has mostly focused on software-based implementations. Real processors don't actually support transactional memory, so it has to be emulated in some way. Some schemes make use of virtual machines to do this—there are transactional memory modifications for the .NET and Java virtual machines, for example—others use native code, and require programmers to use special functions for accessing shared data, so that the transactional memory software can ensure the right things happen in the background. A consistent feature of all of these implementations is that they tend to be slow—sometimes very slow. Although the transactional memory makes it easier to produce bug-free programs, careful use of locks (or other multithreading techniques) can yield much greater performance.

by Peter Bright (http://arstechnica.com/hardware/news/2011/08/ibms-new-transactional-memory-make-or-break-time-for-multithreaded-revolution.ars)