ZiNgA BuRgA Wrote:As said, depends on compressability, but 131MB to 6MB is quite astounding for a general PSP ISO, especially since media (music/FMVs) generally takes up the most space and are often compressed.  Perhaps the game has a fair bit of padding.

ProperBritish Wrote:the first one could compress to 01290, amirite?

hypothetically speaking

Depends what scheme you're using.  For deflate (most popular compression algo, used in ZIP/zlib/gzip and I believe RAR is based on it) there's two stages - a dictionary compress and then an entropy encode.
You'd get something like what you said above with the dictionary phase (it just detects duplicate stuff).  The entropy encode phase would then reduce the above to a few bits.

From what I've read, 7-zip with LZMA2 (v9.xx) generally beats RAR consistently.  Previously, I think RAR was slightly better at handling uncompressed media (eg WAV, BMP etc) than LZMA.
I think PAQ8px is generally considered the best compressor.  KGB is based off PAQ6 or something like that, right?