There is nothing special about QuadDoubler.It is a simple case
of replacing 25 Mhz 040 that came with most Quadras with 40 Mhz
one usually clocked at 2 x 25 Mhz = 50 Mhz .At 040 Macs CPU would
run at system clock externally (fastest system clock is Quadra AV I think
it was 33 Mhz) and at 2 x system clock internally so because of
that some stores would advertise 50 Mhz QuadDoubler as 100 Mhz.
It has fast(er?) memory on the card though and you can add CPU
cache memory to it.
I only noticed some improvement when adding cache myself
Best way to get one is to buy whole Quadra that has one inside.
Somehow you will get it cheaper this way
