Game Pak

Nintendo 64 Game Pak (part number NUS-006) is the brand name of the consumer ROM cartridge product that stores game data for the Nintendo 64, released in 1996. As with Nintendo's previous consoles, the Game Pak's design tradeoffs were intended to achieve maximal system speed and minimal base console cost—with a lesser storage space and a higher unit cost per game. Integrating a CD-ROM drive, with its expensive and slow moving parts, would have drastically increased the console's base price and reduced its performance. The above table is merged from multiple sources and personal knowledge

While the use of the Read and Write contacts seems obvious, it's actually not 100%.

FACTS:

Board  NUS-06A-01  (fully visually confirmable)

Pin 8 (aka write) is routed directly to the save IC, no other stops.

Pin 10 (aka read) is routed to 2 pins of the Game ROM and 1 pin on the save IC

Board NUS-07A-01

Pin 8 (aka write) is routed to 1 pin on the Game ROM (visually confirmable) and 1 pin on the save IC (VM continuity check)

Pin 10 (aka read) is routed to 2 pins of the Game ROM  (visually confirmable) and 1 pin on the save IC (VM Continuity check)

References:

http://n64.icequake.net/mirror/www.crazynation.org/N64/

http://www.acidmods.com/RDC/NINTENDO/N64/N64%20NUS-CPU-03-04.pdf