Quoted from the unit presentation:

The aim of this unit is to provide basic 80-bit extended capabilities for Delphi x64 by providing:

  • A dedicated FPU-backed TExtendedX87 type that behaves as an 80-bit extended value both on 32-bit and 64-bit platforms
  • Re-implementing basic routines from the System unit for this type on 32-bit and 64-bit

Users should be able to either re-declare their variables explictly as TExtendedX87 or redeclare the type extended as
Extended = TExtendedX87;

Freely downloaded from Embarcadero's Code Central.

This unit is very well written. It uses x87 assembly code and operator overloading to provide 80 bit fast computation under Delphi XE2 64 bit compiler.
Most of existing code base on the Extended type can be reused directly, or shared among both 32 bit and 64 bit versions.

Just another gem of Philipp M. Schlüter.
Open Source and Delphi rock!