The original Turbo Freezer, developed in the end 1980ies by Bernhard Engl, was a very neat hardware device plugging into the PBI that allowed you to halt your computer any time, modify memory and to save or restore a complete snapshot to/from disk, extended RAM or cassette. It was a very valuable device both for developers and for gamers.
The goal of this project was to rebuild the original Turbo Freezer using currently available parts, finally we ended up with a largely enhanced device: The new Turbo Freezer XL/XE 2005 is equipped with 512k flash ROM (64k reserved for the Turbo Freezer software, the rest available to the user) and 128k RAM (16k reserved, rest available to the user, can also be used to store snapshots). The free flash and RAM can be used to emulate cartridges (the hardware supports emulation of standard 8k and 16k carts, 16k OSS-type bankswitching carts and 64k SDX style carts). The built-in software was also significantly enhanced, several new functions like block-move/compare/set, value search, load/save snapshots to Turbo Freezer RAM, swap Atari memory with extended RAM/Turbo Freezer RAM contents, control the cartridge emulation, online-help etc. were added
The documentation, software (including source), schematics etc. are available here:
http://turbofreezer.horus.com/
Please note that there are a few minor errors in the schematics, the 00README.txt in the hardware directory contains an errata.
 
The Turbo Freezer XL/XE 2011 is a complete redesign of the previous 2005 model (see below) offering a lot of new exciting features:
Separate, cheap, adapter boards allow you to plug your Turbo Freezer into both an XL and XE computer
Adapter boards are equipped with a PBI passthrough connector so you can still connect PBI devices (like harddrive interfaces)
Xilinx XC95144XL CPLD, a total of 1MB flash memory and 1MB of battery-backed RAM
Built-in battery-backed 512k RAM upgrade (RAMBO compatible, can be enabled/disabled by a switch)
Extended cartridge emulation, adding support for Atarimax compatible banking and stackable SpartaDosX carts
Hardware and software support for Stereo POKEY systems
The documentation, software (including source), schematics etc. are available at the usual location:
http://turbofreezer.horus.com/