IA32e

IA-32e is Intel’s designation for the 64-bit execution environment of the IA-32 (x86) architecture. It corresponds to the x86-64 extension implemented by Intel’s 64-bit processors and was introduced to enable 64-bit computing while preserving IA-32 compatibility. The term appears in Intel manuals to describe the processor’s long-mode operation, contrasted with the traditional 32-bit IA-32 mode.

In IA-32e mode, processors expose 64-bit general-purpose registers, 64-bit instruction pointers, and a 64-bit address space. The architecture uses a four-level paging structure (PML4, PDP, PD, PT) to support virtual addressing, along with the concept of canonical addresses. While the architecture defines a 64-bit address space, practical implementations commonly use a 48-bit virtual address space (with sign-extension rules), and currently supported physical addresses are typically up to 52 bits. Segmentation remains in the architecture but is largely unused for addressing in long mode; code runs with a “64-bit mode” and can also operate in a 32-bit compatibility mode to run existing 32-bit software.

Two primary operating modes exist under IA-32e: IA-32e mode (64-bit mode) for native 64-bit code, and a compatibility mode that allows 32-bit software to run within a 64-bit operating system. This enables mixed environments where older applications coexist with new 64-bit programs.

History and branding: IA-32e originated with Intel’s introduction of EM64T (later renamed Intel 64). The term complements other designations such as x86-64 and AMD64, reflecting Intel’s lineage while emphasizing the 64-bit execution path within IA-32. Over time, Intel vadified the branding toward Intel 64 and x86-64, but IA-32e remains a descriptor found in architectural documentation for the 64-bit extension.