- DVD-R/RW Writability Improvement (further improved from V1.21)
- DVD-R/RW Playability Improvement (further improved from V1.21)
- CD-R/RW Writability Improvement (further improved from V1.21)
- CD-R/RW Playability Improvement
- Supports 2X writing on New Prodisc DVD-R Media
But as many of us already know, you should be really, really careful when upgrading Pioneer's firmware. Pioneer has a legacy of issuing firmware upgrades that wont allow downgrading back to the previous version and that have introduced various limitations on media usage (Pioneer tends to block "unauthorized" blank media manufacturers' discs from burning on its drives). So, beware. Currently the best known firmware for Pioneer A05/105 is v1.20 -- the v1.21 introduced tons of limitations for media use; many x2 discs wont burn at 2x on v1.21, but only at 1x, etc.
More information: Pioneer Australia