When a term like "rootkit" gets enough buzz that the local Sunday paper mentions it you just have to expect vendors to blurt out that they have a solution for it, whether they do or not.
I think this is what happened with Intels recent announcement that they are working on anti-rootkit hardware, a magical rootkit-busting chip.
The technology they describe is certainly interesting and useful, but its not about fighting rootkits.
Intel has two papers I found on their site about the technology, Runtime Integrity and Presence Verification for Software Agents and OS Independent Run-time System Integrity Services. The latter paper is longer and more detailed.
SIS (System Integrity Services), as the name implies, is about protecting the integrity of the system. Thus the purpose of the hardware is to monitor specific code and data areas in the system for activities deemed to be suspicious.
While there are some references in the longer paper to rootkits, its clear that the technique was designed not so much to protect operating systems as security programs.
Its common for malware to attempt to terminate or otherwise interfere with security programs, and Intels SIS would detect this. SIS would also detect buffer overflows in monitored programs attempting to cause arbitrary code execution.
SIS uses the Intel IA-32 System Management Mode (SMM) that was designed for the SL processors almost 15 years ago for reasons, if I remember correctly, to do with power management.
In a sense it acts something like a hardware ICE (In-Circuit Emulator), the gold standard in hardware debugging, to gain absolute control over the use of hardware in the PC.
In this way it can block many software attacks in a clean and tamper-proof way. And because of SMM, it can also monitor for certain hardware-based attacks, such as a malicious device that attempted to inject attack code in the system through DMA (Direct Memory Access), which bypasses the CPU and would therefore bypass any software-based protections.