During my time spent working with multiple machines, I have noticed that performance of the same machine doing the same tasks in the same order differs and sometimes the difference is big enough to be noticeable. This applies to all the machines I've owned and/or maintained (old and modern). Some examples (many of them you may have noticed yourself) that sometimes are completed in different time frames:
- POST
- OS installation
- Hardware tests and operations (usually executed within a customized OS such as one of the many DOS variants), HDD tests and "low level" formats
- Software installation or other tasks (such as benchmarks) within a general purpose OS (Windows, Linux, etc)