ok I tried to double the memory of the installer but nothing changed
I still get that error message on the middle of the instalation of base 12
 bad block type 3
invalid compressed data
format violated 2
and at the start of the install of base 12 it say MKDIR FILE EXIST ?
I have one APPLE partition and 3 AUX partition a swap =  48 meg I have 24
meg of ram in my quadra
and a root partition  and user partition
I download base 12 exacly on the same way as etc witch work in binary mode
with fletch
 I'm using system 7.5