Yes, it does. But I'm not sure, if this is meaning, that Asio4all doesn't work under Windows XP, as it has other architecture, than Windows 7 or Vista.
This article expains it:
http://code.google.com/p/cmediadrivers/wiki/Bitperfect
On the software side, there are some more obstacles: in order to play multiple sounds simultaneously, a so called "kmixer" / "kernel audio mixer" (XP, 2000) respectively "audio service" (Vista) which is part of the sound subsystem of Windows mixes them together and adjusts the volume of the resulting stream. Contrary to popular belief, the kmixer of Windows 2000 and XP doesn't modify the sound and is thus bitperfect if these four conditions are met:
- The PCM/wave volume slider of the mixer (sndvol32.exe) must be set at its maximum. Some start-up applications modify the volume slider (e.g. hardware monitoring tools from Asus).
- The player must be compiled for the same architecture that the OS was compiled for - e.g. 32 bit player on a 32 bit OS, 64 bit player on a 64 bit OS. This is the case for the vast majority of installations because the 64 bit version of Windows XP isn't very commonly used.
- Applications other than the player mustn't play sounds, otherwise the two output streams will be potentially sample rate converted and mixed.
- Applications which are using the soundcard for recording have to use the same sample rate as concurrently running applications which are playing sounds - the soundcard has only one clock generator and hence this limitation arises.
I have also noticed, that when I am playing music over ASIO, and I'm using wave output (onboard audio), wave slider in windows control panel has no effect on sound. But when I play sound without ASIO, wave slider in windows control panel works normaly, and can adjust the sound.
So I think, when four above condictions are met, ASIO works under WindowsXP, and output signal is bitperfect.
