# MOVBE Architecture reference: Feex MOVBE moves an integer between memory and a register while reversing its byte order. It helps convert endianness without changing the processor's general byte-order model. ## What you need to know MOVBE moves an integer between memory and a register while reversing its byte order. It helps convert endianness without changing the processor's general byte-order model. ## How it works MOVBE supports defined scalar operand widths and requires one operand in memory. A load reverses the bytes as data enters a register; a store reverses them as data is written. It is different from a register-to-register BSWAP and is not a memory-copy engine. ## Where it is useful A parser can read a big-endian integer from a network or file format on a little-endian x86 system. Bounds checking and unaligned-access handling still belong to the parser, and byte swapping does not validate the content. ## How to check support and enablement CPUID.01H:ECX bit 22 enumerates MOVBE. Verify the operand width and instruction form needed by the program and compare generated code when investigating a performance difference. Check the exact instruction and operand form rather than inferring support from a neighboring extension. Scalar integer features generally use general-purpose registers; an encoding associated with vectors does not automatically mean a vector-state requirement. ## What the feature does not establish MOVBE does not make arbitrary structures portable across ABIs, repair padding differences or convert floating-point encodings. It does not establish BMI2 or AVX support. A compiler may choose an ordinary load plus byte swap instead. ## Compatibility and performance in practice Correctness depends on edge cases as well as speed. Zero input, overflow, carry flags, operand width, alignment and memory ordering can change semantics. Prefer compiler or library interfaces that document these details and provide a supported fallback. ## A practical verification checklist 1. Record the exact processor or platform model and the application, OS and runtime versions involved. Preserve the wording of the actual error or requirement. 2. Check the manufacturer reference for that exact model, then inspect the effective capability and enabled state in the environment where the program runs. 3. Compare every requirement of the selected binary or backend. A similarly named feature, alias or broad technology label is not enough. 4. Confirm the application selected the intended implementation. Use its documented diagnostics and a supported fallback when requirements are not met. 5. Make one supported change at a time and repeat the same workload. Keep the original configuration and recovery path available. ## If the feature is listed but software cannot use it Start with the exact failing component. A hardware database describes recorded capability; the operating system or hypervisor can expose a different effective environment. An illegal-instruction error also needs investigation of the actual faulting instruction and binary build, because corruption or an unrelated unsupported instruction can produce a similar symptom. Install the application, driver or runtime version supported for the exact platform, and use the vendor's documented baseline or fallback build if needed. A software update cannot create an instruction that the processor lacks. Firmware and security-policy changes should follow the system manufacturer's procedure and a recovery plan rather than a generic optimization recipe. ## Related features and useful distinctions [x86-64-v3](https://feex.it/wiki/hardware/system/x86-64-v3/) · [BMI2](https://feex.it/wiki/hardware/system/bmi2/) · [SSE2](https://feex.it/wiki/hardware/system/sse2/) ## Sources and scope of this explanation [Intel 64 and IA-32 Architectures Software Developer's Manual](https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html) · [x86-64 psABI: processor architecture and microarchitecture levels](https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex) These references establish architectural behavior and software requirements. They do not independently verify every feature value on a linked hardware model page. For model support, use that page's manufacturer evidence and check the effective system configuration. This article does not supply a benchmark, certification or independent review date. ## Related These entities connect to this article. Type is shown on every link. [x86-64-v3: Architecture reference](https://feex.it/wiki/hardware/system/x86-64-v3/)[BMI2: Architecture reference](https://feex.it/wiki/hardware/system/bmi2/)[SSE2: Architecture reference](https://feex.it/wiki/hardware/system/sse2/) ## Sources and verification Editorial ownership: Feex. No independent review date is recorded. [How we research](https://feex.it/wiki/research/). - [Intel 64 and IA-32 Architectures Software Developer's Manual ](https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html)· Volumes 1 and 2 describe the named instruction families and CPUID; Volume 3 describes state, paging, VMX and protection controls. Architecture documentation does not establish support for a particular model. - [x86-64 psABI: processor architecture and microarchitecture levels ](https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex)· Machine Interface, Processor Architecture: baseline and cumulative v2/v3/v4 feature table, OS-state checks and deployment recommendations. [Report a correction to Feex](https://feex.it/contact/) ## Was this article useful? A yes or no is enough. Pick a reason if you want, or add a short note. Quick facts The short identity of this page. Specs, sources, and the full story stay in the article. --- Source: [Canonical Feex Wiki page](https://feex.it/wiki/hardware/system/movbe/) [Developer guide](https://feex.it/wiki/developers/) | [API policy](https://feex.it/developers/api-policy/) | [Agent guidance](https://feex.it/wiki/llms.txt)