Atari 1400XL

Originally called the 1201XL (as it was meant to be a replacement to the 1200XL and used the same case and keyboard), the Atari 1400XL was the next revision of the 800XL hardware. 

One of its new features were 2 new chips - a custom MCU (Memory Control Unit) chip called FREDDIE (a DRAM controller which was an enhanced consolidation of TTL chips found in earlier XL's) and the CO61618 MMU (Memory Management Unit).  Together, they handled bank-switching functions and improved memory management by allowing the CPU to access memory for programs (up to 64K) and the ANTIC to  access up to 8K or more if needed to display graphics.  The next major addition was a built-in 300 Baud modem.  The last new feature was a SC-01 speech synthesizer chip which included modifications to the OS to allow for a V: handler for VOICE.  The system was to include a 1400XL Telecommunicator cartridge that allowed you to use the synthesizer to announce changes in the program's configuration.

The original 1400XLs produced have motherboards that are marked "1400" on them.  Atari later decided created the "1450" motherboard that was intended to be used for both the 1400XL an 1450XLD as it included power and PBI daughter card connectors for the addition of disk drives.