The 68040 CPU is fitted on the A3640 processor-card,
wich is standard in the A4000(T). There's no standard
020 in the A4000(T). However, some A4000's where equiped
with 030 CPU's.
According to the bboah Commodore released a few 020 equipped A4000s.. and theres even a "020" jumper on the A4000 mainboard..
