According to Plextor tech support the 1.01 firmware for the 40x CD Rom has the following improvements :

Fixes:
1. Correction of INDEX data for READ SUBCHANNEL command
2. Correction of TRACK LENGTH data for READ TRACK INFORMATION command
3. Correction of execution of START/STOP UNIT command in certain cases


4. Readability of SMALL 2nd session of CD Extra disc
5. Readability of BEGINNING of 2nd session of multisession disc
6. Readability of gab between DATA and AUDIO track
7. Playability of CD Extra disc under Windows 3.51