Hi --
Not too much to add to what Michael and Joe have said. Thanks, guys!
From the hardware perspective, the original "AWM" hasn't been deployed in a Yamaha product for a zillion years. (Please see the Yamaha history in Michael's post). I remember reading (Yamaha synth forum?) where marketing has been using "AWM" and "AWM2" interchangeably in recent years, both meaning AWM2.
The sound generation chip (SWP51) in the first gen MX is the same as the Motif XS and XF, MOX and MOXF, Tyros 4 and 5, S750 and S950. The newer Yamaha products use the newest chip (SWP70). That would be Montage, Genos, S770 and S970, S775 and S975.
I have not seen a service manual for the second generation MX, but I suspect that it uses the SWP70, too. A hardware refresh was required because the SWP51L is out of production and the SWP70 is the mainline tone generator chip.
Much of the AWM2 technology is incorporated at the chip level -- the sample decompression is done on the fly from dedicated waveform memory. Filtering and other magic is done on the fly, too, in order to reduce latency.
I play and have compared MOX6 and S950. If there are sound differences, it's due to voice and DSP programming. Architecturally, the Motif XS, XF, MOX, MOXF allow two insert DSPs in series/parallel while arrangers are limited to one insert DSP per voice. That is one of the few fixed factors that are different between the software+hardware engines.
Hope this helps -- pj
P.S. As Joe mentioned, the MX is the value product in the three tier Montage, MOXF, MX product stack. BTW, the MOXF is also due for a refresh.