[vikingerik]

It's not clear if we're talking consistently about the sizes. If 15-20s is referring to a 7800 cartridge that's up to 48kb, that makes sense. This subthread is talking about 2600 games up to 4kb.

Also it's not clear how the console reads cartridges with bankswitching hardware. It can't really know if a cart has that. So it may just have to try all the common schemes on every cart, and read through the entire ROM space multiple times in case anything changed. That would account for the timing.