Brian A. Davis wrote:
On all of my A2 motherboards there is a 9334
chip. After I did some searching, I found reference that the 9334 is an
8-bit addressable latch. This is the same description as the 74LS259.
Apple obviously just used a different part that does the same job.
The 9334 is a Fairchild part number and is equivalent to the 74259
(standard TTL) according to my Nat Semi databook. This may give
slightly higher drive to the annunciators AN0..AN3. My II+ motherboard
is marked with 9334 and has a DM9334N (Nat Semi) in the socket.
The typical total power dissipation for the three chips is:
DM9334 280mW
DM74259 150mW
DM74LS259 110mW