According to item j in: http://www.softarch.com/us/products/WriteCDRW/mtrainierfaqs.html
legacy CDRW drives will not be able to write in Mt. Rainier
format. Is this because Mt. Rainier format is set up
(purposely) in such a way that even special software on legacy
drives couldn't emulate writing to it, or is it that the
drive/software makers are too lazy or deem that there's no market
Let say that since Mt. Rainier has a minimal granularity of 2K
bytes and legacy drives support only 64K byte writes, there's
no reason why emulation software on legacy drives cannot read
a 64K chunk, modify 2K of it, then write the 64K chunk back, to
emulate a 2K write. With intelligent caching, the performance
can even get better much better than this.
It'll be quite a while before I fully switch to Mt. Rainier
format if I know that my legacy CDRW drives are going to be
left in the dust as far as writing is concerned. Especially
if CDRW write speeds keep increasing (16x now) so format time
decreases even in old-UDF mode.
The price for progress...