Altiverb 6 Regular

-Windows: VST, RTAS and Audio Suite.
-Mac OS X: VST, MAS, Audio Unit, RTAS and Audio Suite, Universal Binaries for both Power PC and Mac-Intel
-The Full Altiverb Impulse Response library
-Full parameter automation
-an impulse response browser that replaces the impulse response popup menu.
-mono to mono, mono to stereo, and stereo to stereo channel configurations.
-supported sample rates up to and including 96 kHz.
-40 snapshot memories for total-recall via parameter automation.
i-Lok or Challenge-Response authorization.
-Sample your own spaces or gear (Mac only)

Altiverb 6 XL
this version adds to Altiverb 6 Regular:

-All channel configurations up to 5.1 surround.
-TDM support, on Mac OS X Pro Tools | HD Accel DSP chips. (support for regular HD chips scheduled for a later release). TDM sample rates supported: 44.1 kHz, 48 kHz, 88.2 kHz and 96 kHz
-zero TDM latency at 44.1 kHz and 48 kHz. At 96 kHz sample rate 0.2 milliseconds latency (0.0002 seconds or 200 samples)
-supported sample rates for RTAS, VST, AU, MAS and Audio Suite up to and including 384 kHz.