However, many programs, some even formerly sold by Atari, do not jump through published jump vectors when using the operating system. The 130XE has an extra 64K bank of memory. It is divided into four blocks of 16K each. The phase 2 clock runs at 1.8 MHz. The clock goes from high to low, when the data lines are also valid.
All lines then become invalid.
The 130XE doesn't have the parallel port. However, it has a cartridge slot expansion. It is set up when a channel is opened to the screen. It is used to restore the display if DMA is disabled. This part of the operating system ROM is disabled when not used.